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The Third International Conference on Computational Science and Engineering (ICCSE-3)28-30 November, 2016, Ho Chi Minh City, Vietnam

INVITED TALKS

1


I2.1

Recent Advances in Long-range Corrected (LC) DFT

KIMIHIKO HIRAO

Advanced Institute for Computational Science, RIKEN, Kobe, JapanE-mail: [email protected]

DFT has emerged as a powerful computational tool for the chemical systems. It is simple and conceptual. KS-DFT calculation takes about the same amount of time as a Hartree-Fock (HF) calculation, yet unlike HF, we get a correlated result from KS-DFT. Many of the problems of KS-DFT have mostly been a consequence of not having accurate functionals and potentials. Recently there has been considerable interest in the long-range corrected (LC) DFT. In the LC scheme the exchange functional is partitioned with respect to the inter-electronic separation into long-range and short-range parts using a standard error function. The LC solves many of DFT problems: LC remedies the underestimation of Rydberg and core excitation energies and corresponding oscillator strengths, the poor reproduction of charge-transfer excitations in TD-DFT calculations, and the overestimation of linear and nonlinear polarizabilities of long-chain molecules in CP-DFT calculations. The LC successfully provides a good description of weak van der Waals interactions as well as accurate reaction enthalpies and barrier heights. The LC satisfies Koopmans’ theorem, which implies that the eigenvalues and eigenvectors connected to the Kohn-Sham equation have a strict physical meaning. The expensive time cost to evaluate the long-range HF exchange is a big obstacle to be overcome to be applied to the large molecular systems and the solid state materials. Upon this problem, we propose a linear-scaling method of the HF exchange integration, in particular, for the LC-DFT hybrid functional. Recent advances in LC-DFT will be discussed.

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I2.2

Structural Variations and Chemical Bonding in Platinum Complexes of Group 14 Heavier Tetrylene Homologues. Do Divalent Tetrylenes(II) have Hidden Divalent Tetrylones(0)

Chemistry Character?

NGUYEN THI AI NHUNG

Department of Chemistry, Universit of Hue, Hue, VietnamEmail: [email protected]

The structures of Pt(II) complexes containing the heavier homologues of germylene, stannylene, and plumbylene [PtCl2−{NHEMe}] (Pt−NHE) with E = Ge to Pb, in which the ligand {NHEMe} retains one lone pair at the E central atom as called heavier tetrylenes, have been computed using density functional theory calculations at the BP86 level with def2-SVP, def2-TZVPP, and TZ2P+ basis sets. The bonding of the complexes has been analyzed by charge and energy decomposition analysis methods. The results of bonding analysis show that NHEMe ligands exhibit donor-acceptor bonds with the lone pair electrons of heavier NHEMe

donated into the vacant orbital of the metal fragment, and the Pt−E bonds having PtCl2←NHEMe strong -donation. The divalent heavier tetrylenes(II) have the same role as the divalent heavier tetrylones(0) character since the ligand can retain the two lone pairs at E atom. Currently experimental efforts are directed towards the synthesis of tetrylenes Pt(II) complexes from natural products. Hence, the results in this study will provide an insight into the properties and chemical bonding of complexes being synthesized.

E = Ge, Sn, Pb

Scheme 1: Overview of the compounds investigated.

Keywords: Density functional calculations, Bonding analysis, Carbenes, Germylenes, Stannylenes, Plumbylenes, Platinum.

3

(a) [PtCl2-{NHEMe}] (Pt−NHE) (b) NHEMe (NHE)


I2.3

Stepwise Double Excited-State Proton Transfer Is Not Possible in 7-Azaindole Dimer

NAWEE KUNGWAN

Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand

Email: [email protected]

The nature of the excited-state double proton transfer in 7-Azaindole (7AI) dimer—whether it is stepwise or concerted—has been under a fierce debate for two decades. Based on high-level computational simulations of static and dynamic properties, we show that much of the earlier discussions was induced by inappropriate theoretical modelling, which led to biased conclusions towards one or other mechanism. A proper topograhical description of the excited-state potential energy surface of 7AI dimer in the gas phase clearly reveals that the stepwise mechanism is not accessible due to kinetic and thermodynamic reasons. Single proton transfer can occur, but when it does, an energy barrier blocks the transfer of the second proton and the dimer relaxes through internal conversion. Double proton transfer takes place exclusively by an asynchronous concerted mechanism.

References [1] Chemical Science, 2015, 6(10), 5762-5767

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I2.4

Bridging Fundamental Chemistry/Physics and Reaction Engineering - Applications and Computational Tools

LAM K. HUYNH

Department of Applied Chemistry, International University, Vietnam National University – HCM City


Computational modeling/simulation has served not only as a powerful post-facto tool for validating existing principles and knowledge but also a strong predictive tool in the discovery of new knowledge in science and engineering. Recent advances in information technology, algorithm, and scientific methods, which allow faster and more accurate calculations for more realistic systems, have laid a solid foundation for bridging the time and length scale from fundamental science to real engineering challenges. In this talk, I will demonstrate how to bridge fundamental chemistry/physics & reaction engineering modeling in two domains/aspects: (1) gas-phase chemistry and (2) complex chemical processes on surfaces (catalyst/material design). In gas-phase chemistry, an example for understanding and modeling low-temperature combustion of hydrocarbon and alternative fuels will be discussed in detail. Next, I will demonstrate how to design better catalysts for complex chemical systems such as methanol conversion and water-gas shift reactions on Ni nanocatalysts. To facilitate the multiscale applications, I will briefly present main features of our in-house computational tools, namely MultiSpecies-MultiChannel1 (MSMC) for complex gas-phase systems and Surfkin2 for gas-surface reactions.

Keywords: Multiscale, Modeling, Simulation, Gas-phase Chemistry, Materials Design, Thermodynamics and

Kinetics

References

[1] Duong, M. V.; Nguyen, H. T.; Truong, N.; Le, T. N. M.; Huynh, L. K. Multi-Species Multi-Channel (MSMC): An Ab Initio-based Parallel Thermodynamic and Kinetic Code for Complex Chemical Systems. Int. J. Chem. Kinet. 2015, 47 (9), 564-575; https://sites.google.com/site/msmccode/

[2] Le, T. N.; Liu, B.; Huynh, L. K. SurfKin: An ab initio kinetic code for modeling surface reactions. J. Comput. Chem. 2014, 35 (26), 1890-9.

5


I2.5

Skeletal Mechanisms Relevant to the Formation of Unsaturated Intermediates in Combustion of Methyl Ester Fuel Surrogates

FAN-HSU KAO,1 HAIRONG TAO,2 KUANG C. LIN 1

1 Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan

2 College of Chemistry, Beijing Normal University, Beijing, 100875, ChinaEmail: [email protected]

In this study, a skeletal kinetic mechanisms for biodiesel fuel surrogates is developed for fuel oxidation that can overcome the barrier of incorporating detailed chemistry to computational fluid dynamics (CFD) for fuel combustion. This study begins from assembling mechanisms which are able to predict experimentally measured methyl isobutyrate (MIB), polycyclic aromatic hydrocarbons (PAHs) and compound (C5H10). Then, we generate a minimized skeletal mechanism using the path flux analysis method that determines a trade-off between the accuracy and mechanism size. The newly derived compact mechanisms are examined in ignition delay time in 0-D shock tube modeling, 1-D premixed burner flame, 1-D counterflow diffusion flame, and 2-D laminar diffusion flame. We carry out the error analyses introduced by the removal of species and reactions from the detailed mechanism. The rate of production (ROP) and sensitivity analysis (SA) are used to improve the predictions of skeletal mechanisms. Moreover, the revised MIB skeletal mechanism are selected to be combined with the soot sub model to obtain a skeletal mechanism which is able to predict the heavy PAHs and soot formation in pure methane flame and methane/air diffusion flame doped with MIB.

Keywords: Biodiesel, Chemical Kinetic, Combustion, Computational Fluid Dynamics, Methyl Ester, Mechanism Reduction, Polycyclic Aromatic Hydrocarbons, Soot.

6


I2.6

Mechanisms and Kinetics of Some Reactions Related to Atmospheric and Combustion Chemistry

NGUYEN THI MINH HUE

Faculy of Chemistry and Center for Computational Science, Hanoi National University of Education, 136 Xuan Thuy, Cau Giay, Hanoi, Viet NamEmail: [email protected]

In this talk we present our recent results obtained using both high accuracy molecular orbital and density functional methods to determine the potential energy surfaces, and the kinetics and mechanisms of a series of gas phase reactions involving small organic species and related to the atmospheric chemistry and combustion processes.

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I2.7

Computational Design for Advanced Materials in Environmental Applications

SUPAWADEE NAMUANGRUK

Nanoscale simulation laboratory (SIM), NANOTEC, National Science and Technology Development Agency, Klong Luang, Pathum Thani 12120, Thailand

E-mail: [email protected]

Understanding insight to the molecular level of chemical processes in nanomaterials is a key of development of nanomaterials for specific purpose. Generally, the development of nanomaterials is essential in novel technologies to address challenges related to the production, storage and efficient use of energy, as well as environmental applications. However, the design, development and commercialization of a new material can take several years. To accelerate functional material development, molecular simulation is a powerful tool that can help explore the nanomaterial at a significantly faster rate and lower cost than it can typically be done experimentally. This helps experimentalist focus only on the most promising materials. Here, deep understanding of the adsorption and reaction mechanism of toxic compounds at nanoscale are shown by molecular modelling and simulations. Through computational design and calculation, promising materials were suggested, such as catalysts for NOx decomposition as well as adsorbents for elemental mercury (Hg0) removal, before they are synthesized by experimentalist.

Figure 1. Understanding synergetic effect of TiO2-supported silver nanoparticle as a sorbent for Hg0 removal

References [1] Rungnim, C; Hannongbua, S; Promarak, V; Kungwan, N; Namuangruk, S. J. Hazardrous Mater. 310 (2016)

253-260. [2] Rungnim, C.; Meeprasert, J.; Kunaseth, M.; Junkaew, A.; Khamdahsag, P.; Khemthong, P.; Pimpha, N.;

Namuangruk, S. Chem. Eng. J, 274 (2015) 132-142. [3] Maitarad, P; Meeprasert, J.; Han, J.; Shi, L.; Limtrakul, J.; Zhang, D.; Namuangruk, S. Catal. Sci. Technol.

2016, DOI: 10.1039/C5CY02116B[4] Meeprasert, J.; Junkaew, A.; Rungnim, Meeprasert, J.; C.; Kunaseth, M.; Namuangruk, S. Appl. Surf. Sci.,

364 (2016) 166–175.

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I2.8

Ab-initio Methods for Time-Resolved Attosecond Dynamics of Laser-Driven Many-Electron Molecules

THANH TUNG NGUYEN-DANG

Département de Chimie, Université Laval, Québec, G1K7P4, Qc, CanadaEmail: [email protected]

Ultrafast spectroscopic and imaging schemes using short and intense laser pulses hold great promises in Chemical Physics, as the matching of the durations of these pulses with the characteristic periods of molecular motions means that one can take snapshots and videos of these motions on their natural time-scales. Molecular and/or electronic processes unfolding under an ultrafast intense laser pulse are highly non-linear however, and their descriptions require new non-perturbative theoretical and computational tools to be developed. After reviewing these new challenges in theoretical chemistry, we will focus on the description of time-resolved multi-electron, attosecond dynamics by an ab-initio approach, highlighting in particular the way a number of powerful tools of stationary-state Quantum Chemistry can be adapted to suit the new context, that of time-dependent non-perturbative electron dynamics. Results of calculations on a number of few electron systems, in particular ionic-channel-resolved photoelectron spectra resulting from strong field molecular ionizations under a few-cycle NIR and/or XUV pulse, will be shown to illustrate the concepts and methodological ideas developed throughout the talk.

Keywords: Time-Dependent Quantum Mechanics, Electron Dynamics, Intense-Field Ionization, TDCI, Feshbach Partitioning

9


I2.9

Inclusion Complexation of Insoluble Compounds with Cyclodextrins

THANYADA RUNGROTMONGKOL

Structural and Computational Biology Research Group, Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand


Pinostrobin is widely found in the ginger family and adopted in traditional Thai medicine, while fisetin is abundant in strawberry and mango. Besides the known antioxidant and anti-inflammatory properties of flavonoids, pinostrobin shows the HIV-1 and HSV-1 antiviral activity and cytotoxic activity against tumor cells. Fisetin has the cancer preventive properties and potential therapeutic use for the diabetic treatment. However, these flavonoids show relatively low solubility and low physicochemical stability, leading to difficulties in pharmaceutical and biomedical applications. By complexation with cyclodextrin, the solubility enhancement of pinostrobin and fisetin is our main aim. Both experimental and theoretical approaches are applied. The complexes between flavonoid and various cyclodextrins (both natural and modified cyclodextrins) are prepared, and followed by measurement of the spectroscopic details and thermodynamics properties (1-3). The solubility of the inclusion complexes is determined in comparison with the flavonoid alone. Besides the complex geometry obtained from experiments, the molecular dynamics simulations are performed in order to investigate the structure and stability of inclusion complex, as well as intermolecular interaction between each flavonoid and cyclodextrin (4,5). In addition to the pharmaceutical and biomedical benefits, the results of this research would increase the values of both flavonoid and cyclodextrin which are rich natural resources in Thailand with a consequence of local economy development.

Keywords: Inclusion complex, Interaction, Stability, Anticancer activity

References[1] Sangpheak W., Khuntawee W., Wolschann P., Pongsawasdi P. and Rungrotmongkol T. “Enhanced stability

of naringenin/2,6-dimethyl β-cyclodextrin inclusion complex: Molecular dynamics and free energy calculations based on MM- and QMPBSA/GBSA” J. Mol. Graph Model, 50 , 10–15 (2014).

[2] Sangpheak W., Kicuntod J., Schuster R., Rungrotmongkol T., Wolschann P., Kuawan N., Viernstein H., Mueller M. and Pongsawasdi P. “Physical properties and biological activities of hesperetin and naringenin in complex with methylated β-cyclodextrin” Beilstein J. Org. Chem., 11, 2763–2773 (2015).

[3] Rungnim C., Phunpee S., Kunaseth M., Namuangruk S., Rungsardthong K., Rungrotmongkol T. and Ruktanonchai U. “Co-solvation effect on the binding mode of the α-mangostin/β-cyclodextrin inclusion complex” Beilstein J. Org. Chem., 11, 2306–2317 (2015).

[4] Nutho B., Khuntawee W., Rungnim C., Pongsawasdi P., Wolschann P., Karpfen A., Kungwan N. and Rungrotmongkol T. “Binding mode and free energy prediction of fisetin/β-cyclodextrin inclusion complex” Beilstein J. Org. Chem., 10, 2789–2799 (2014).

[5] Kicuntod J., Khuntawee W., Wolschann P., Pongsawasdi P., Kuawan N. and Rungrotmongkol T. “Inclusion complexation of pinostrobin with various cyclodextrin derivatives” J. Mol. Graph Model, 63, 91–98 (2016).

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http://pubs.rsc.org/en/results?searchtext=Author%3AAlfred%20Karpfen

http://www.sciencedirect.com/science/journal/10933263/50/supp/C

http://www.sciencedirect.com/science/journal/10933263/50/supp/C


I2.10

Theoretical Rate Coefficient Calculation for Reactions of Criegee Intermediate with Atmospheric Trace Gases

FRANK YIN, KAITO TAKAHASHI* Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan


Atmospherically relevant carbonyl oxide R1R2COO, so-called Criegee intermediates (CIs), can have many different forms depending on the substituents R1 and R2. These strong oxidizing species are the key intermediate in the ozonolysis of different kinds of alkenes in the atmosphere. Due to CI’s active participation in atmospheric chemistry, such as oxidation, aerosol formation and OH radical production, the atmospheric fate of this very reactive species is a very important topic. However, presently there are no effective methods to measure the CI concentration in the atmosphere. Thus the only way to know the CI concentration is through the rate of its production and removal. Considering the abundance of water in the atmosphere, the reaction rate of CIs and water vapor is a very important quantity to accurately model the removal rate of CI. In this study we theoretically calculated the rate coefficient of the reaction between CI and atmospheric trace gases such as water vapor. By comparing the results for (CH3)2COO as well as CH3CH2CHOO versus those for CH3CHOO we evaluate the effect attaching additional methyl substitution in C3 CIs. Furthermore, by studying the reaction for CH2CHCHOO and CHCCHOO with water vapor, we evaluate the effect of the pi conjugation toward the reactivity.

11


I2.11

Theoretical Study on the Catalytic Reduction Mechanism of NO by CO catalyzed by Ag7Au6 Cluster

SIRIPORN JUNGSUTTIWONG, 1 YUTTHANA WONGNONGWA,1 SUPAWADEE NAMUANGRUK2

1Department of Chemistry andCenter of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190, Thailand.

2National Nanotechnology Center, National Science and Technology Development Agency,Klong Luang, Pathumthani 12120, Thailand


The reaction mechanism of NO catalyzed by CO on Ag7Au6 cluster has been systematically investigated on the ground and first excited states at the PBE/TZVP, lanl2dz level. This reaction is mainly divided into two reaction stages, NO deoxygenation to generate N2O and then the deoxygenation of N2O with CO to form N2 and CO2. The crucial reaction step deals with the NO deoxygenation to generate N2O catalyzed by Ag7Au6 cluster, in which the deoxygenation of NO by CO reaction pathway is kinetically more preferable than that in the absence of CO. These results can qualitatively explain the experimental finding of N2O, N2, NCO and CO2 species in the NO by CO reaction.

Figure 1. The energy diagrams for the NO deoxygenation with CO catalyzed by Ag7Au6 Cluster

Keywords: catalytic reduction, NO by CO reaction, Ag7Au6 cluster

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mailto:[email protected]


I2.12

Structural Evolution in Methylammonium Lead Iodide CH3NH3PbI3

KHUONG P. ONG ,1 TECK WEE GOH,2 GIANG XU,2 ALFRED HUAN1

1 Institute of High Performance Computing, Agency of Science, Technology and Research (A*STAR), 1 Fusionopolis Way, 138632, Singapore

2 Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, 637371 Singapore


AbstractWith the average growth of 40 percent per year, solar energy has been growing at a remarkable rate. The prospect for sustaining such growth is based on the possible constraints on materials availability. Recently, the organometal lead halide hybrid perovskite, with main focus on methylammonium lead iodide perovskite (MAPbI3), has been identified as a suitable candidate for use as active material in solar cells. Solar cell performance using this material has seen tremendous progress, from power conversion efficiency of 3.8% to over 20% in a relatively short time of dedicated photovoltaic research. Theoretical and experimental researches have achieved much of progress in understanding electronic structures, chemical bonding, Rashba effect toward to optimizing the best performance for MAPbI3. In this work, through first principle calculations we identify the mechanical origin of the structural evolution and the interplay between the various MA cation orientations in the methylammonium lead iodide perovskite (MAPbI3) to the band structures and optical properties of MAPbI3. Our study provides clear understanding for the structural phase transitions and their influence on the performance of MAPbI3

Figure 1. Structural evolution in MAPbI3

Keywords: hybrid perovskite, photovoltaics, density functional theory, phase transitions, optical properties

13



I2.13

First Principles Study of Hydrogen Production and Storage

NACHIMUTHU SANTHANAMOORTHI, HSIN-NI CHIANG, PO-JUNG LAI, JYH-CHIANG JIANG

Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, 106, Taiwan


AbstractIn the current energy research, hydrogen, the most abundant element in the universe is considered as a “green fuel” because, it burns cleanly without emitting any environmental pollutants and is considered as a most viable energy source. H2 can be produced from different sources, e.g., coal, natural gas, liquefied petroleum gas (LPG), propane, methane (CH4), dry biomass, biomass-derived liquid fuels (such as methanol, C2H5OH, biodiesel), as well as from water. Among the liquid H2 sources, C2H5OH and water are good candidates due to its low toxicity and easily available in nature etc,. Here we proposed H2 production from steam reforming by C2H5OH. Steam reforming is the first step of the H2 production process involves a light hydrocarbon reacting with steam. The second step, known as a water gas shift (WGS) reaction, the CO produced in the first reaction is reacted with steam over a catalyst to form H2 and CO2. We used DFT methods to investigate the mechanism of the WGS reaction on a model consisting of 3Cu atom-cluster on an 3Cu/α-Al2O3(0001) surface. Here we propose three reaction mechanisms, such as redox, carboxyl and formate, have been examined and we found that the H2

formation barrier is extremely low, 0.65 eV, on this surface. However, storage of hydrogen under appropriate conditions is the challenging problem in the modern research. In this present study we propose a new strategy in which we considered three transition metal (TM) atoms with high, medium and low hydrogen adsorption energies. These TM atoms are used to decorate the Boron doped graphene sheet and our results show that the activation energies for H atom diffusion are much smaller than the previously reported values, indicating that a fast H diffusion on this proposed surface can be achieved.

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I2.14

Square-Triangle Solid-Solid Phase Transition in 2D Simple System

VO VAN HOANG

Computational Physics Lab, HCM City Univ. of Technology, Vietnam National Univ. HCM City, 268 Ly Thuong Kiet Street, District 10, HCM City, Vietnam


Square-triangle solid-solid phase transition in 2D simple monatomic system is studied by molecular dynamics (MD) simulation in models containing 6400 particles interacted via square potential [1]. Initial equilibrium models with a square lattice structure obtained at low temperature are compressed step by step and we find a square-triangle solid-solid phase transition in the system. Evolution of structure and various thermodynamic behaviors upon compression is analyzed in details in order to study atomic mechanism of this solid-solid phase transition. We find a quite new mechanism of formation of new phase (triangular one), i.e. nucleation of new phase is not homogeneous. Atoms involving in triangles do not occur homogeneously throughout in the model, instead, they form some separated domains in the parent phase. Further growth of these domains together with formation/growth of new ones leads to the percolation of new phase. Our detailed MD simulation highlights the situation related to the role of ‘liquidlike’ atoms in the nucleation of solid-solid phase transition found recently [2,3]. Solid-solid phase transitions are important in science and technology including the earth science, diamond and steel production or synthesis of ceramic materials, however, understanding of nature of these important phase transitions at the atomic level is still poor. Therefore, detailed MD simulation in this direction is of great interest.

References[1] M. Rechtsman et al., Phys. Rev. E 73, 011406 (2006).[2] Yi Peng et al., Nature Mater. 14, 101 (2015).[3] D.M. Hatch et al., Phys. Rev. Lett. 115, 185701 (2015).

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CONTRIBUTED TALKS

16


O2.1

Geometrical and Electronic Structures of MnSn−/0 (n =1 - 3)

Clusters from Computational Chemistry and Anion Photoelectron Spectroscopy

VAN TAN TRAN , QUOC TRI TRAN

Department of Chemistry, Dong Thap University, Cao Lanh City, Dong Thap, Viet Nam


The geometrical and electronic structures of the MnSn−/0 (n = 1 - 3) clusters were probed by the photoelectron

spectroscopy a long time ago.[1] {Zhang, 1996 #391} However, the reported photoelectron spectra are not fully understood. In this work, the geometrical and electronic structures of MnSn

−/0 (n = 1 - 3) clusters are investigated with the B3LYP functional, ROHF/CCSD(T), CASSCF/NEVPT2, and CASSCF/CASPT2 methods.[2-4] The relative energies, structural parameters, and harmonic vibrational frequencies and normal modes of the low-lying states of the most important isomers of the studied clusters are reported. Also, the electron detachment energies of the anionic clusters are calculated. Based on the computational results, the photoelectron spectra of MnS−, MnS2

−, and MnS3− are interpreted. The low-lying bands in the photoelectron spectra of MnS− cluster are

assigned to the electron detachments from the 7Σ+ anionic ground state. All features in the photoelectron spectra of MnS2

− cluster are ascribed to the electron detachments from the 5Πg of the most stable linear SMnS− isomer and from the 7A1 of the meta stable cyclic η2-MnS2

− isomer. The photoelectron spectra of MnS3− cluster are

explained by the electron detachments from the most stable η2-(S2)MnS− and from the less stable η2-(S3)Mn−

and triangle MnS3− isomers. The Franck-Condon factor simulations based on the B3LYP geometrical structures

and harmonic vibrational frequencies and modes confirm the shapes of the low-lying bands in the photoelectron spectra of MnSn

− (n = 1 - 3) clusters.

Figure 1. Geometries of the low-lying isomers of MnSn−/0 (n = 1 - 3) clusters

Keywords: MnSn−/0 (n = 1 - 3) clusters, geometrical structure, electronic structure, CASPT2, DFT

References[1] N. Zhang, H. Kawamata, A. Nakajima, K. Kaya, J. Chem. Phys. 1996, 104, (1), 36.[2] V.T. Tran, Q.T. Tran, M.F.A. Hendrickx, J. Phys. Chem. A 2015, 119, (22), 5626.[3] V.T. Tran, Q.T. Tran, J. Phys. Chem. A 2016, 120, (20), 3670.[4] V.T. Tran, Q.T. Tran, M.F.A. Hendrickx, Chem. Phys. Lett. 2015, 627, 121.

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O2.2

Data-Mining and Machine-Learning in Materials Science

PHAM TIEN LAM , 1, 2, 3, DAM HIEU CHI1, 3, 4, 5

1Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan2Institute for Solid State Physics, The University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8581,

Japan3ESICMM, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan

4Center for Materials Research by Information Integration, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan

5JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, JapanEmail: [email protected]

Recently, the increasing volume of available experimental and quantum computational materials databases together with the development of machine learning techniques open up a new opportunity to build automatic methods for discovering new materials and new phenomena. In this talk, we give a short overview of the application of data mining and machine-learning in material science. We discuss how machine learning can be applied in predicting physical properties, finding the mechanism of a property or function (structure-property relationship modeling), and exploring and visualizing in materials space. In order to apply machine-learning algorithms materials science issues, we focus on the methods for encoding materials and finding materials similarity. Our research demonstrates that knowledge of chemical physics on a materials system can be automatically extracted from the experimental or calculated data using data mining techniques. Dimensional reduction algorithms, e.g. principle component analysis (PCA) and manifold learning, is employed to discover the low-dimensional embedding and the high-dimensional data. This new representation is used to visualize the materials space and to find the pattern of material systems. It is shown that the machine-learned knowledge can be utilized to construct simple models for predicting physical properties of a chemical system. By using advanced regression algorithms, the parameters determining physical properties is derived from materials datasets.

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O2.3

A Theoretical Investigation on Interactions of Cisplatin and a Novel Derivative with the Nucleobase Guanine

PHAM VU NHAT

Department of Chemistry, College of Natural Sciences, Can Tho University, Can Tho, Viet Nam


Quantum chemical calculations are employed to examine the interactions of hydrolysis products of cisplatin and a novel derivative cis-[PtCl2(iPram)(Hpz)] with the purine base site of DNA using guanine as a model reactant. Thermodynamic parameters, electronic structures, bonding characteristics and spectroscopic properties of the resulting complexes are investigated in the framework of density functional theory (B3LYP functional) along with correlation consistent basis sets. Computed results show that these interactions are dominated by electrostatic effects, namely H-bond contributions, and there exists a flow charge from H atoms of ligands to the O6 guanine. Another remarkable finding is that the replacement of amine groups by larger ones accompanies with a moderate reaction between PtII and guanine molecule.

Figure 1. Vibrational signatures of [Pt(iPram)(Hpz)(H2O)Cl]+ (above) and [Pt(iPram)(Hpz)(G)Cl]+ (below) in their lowest-lying states

Keywords: Cisplatin, Density Functional Theory, Guanine, Anticancer, Hydrogen Bonding

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O2.4

Density Functional Theory Modeling of Luminescent Properties of Oligoatomic Silver Clusters in LTA Zeolite

NGO TUAN CUONG, 1 PHAM HO MY PHUONG,2 NGUYEN THI MINH HUE1

1Faculty of Chemistry and Center for Computational Science, Hanoi National University of Education, Vietnam2 Institute for Computational Science and Technology, Ho Chi Minh City, Vietnam


Optical spectra in the UV-VIS region of the hydrated doubly charged tetramer Ag42+ and hydrated multiply

charged hexamer Ag6p+ silver clusters encapsulated inside the sodalite cavity of LTA-type zeolite have been

systematically investigated using DFT, TD-DFT and CASSCF/CASPT2 methods. Absorption spectrum of Ag42+

(H2O)m cluster in sodalite cage reproducing the experimental absorption spectrum in the region from 300 to 600 nm. The average lengths of Ag-Ag and Ag-OH2 bonds are in good agreement with EXAFS results. The water environment forces the silver tetramer to relocate in one side of the cavity instead of at its center as in the case of non-hydrated [Ag4(Si24H24O36)]2+ cluster, and acts as ligands significantly splitting the energy levels of excited states of the clusters. This causes the absorption spectra of the clusters to broaden and the emission to shift to the green-yellow and red part of the visible region.

20


O2.5

Physical Insights of Coadsorption SO2 and CO2 in Metal–Organic Framework Material Ni(bdc)(ted)0.5

DO NGOC SON , TA THI THUY HUONG

Ho Chi Minh City University of Technology, VNU-HCM, Ho Chi Minh City, Vietnam


Metal organic framework Ni(bdc)(ted)0.5 is a promising material for the simultaneous capture and reduction of the harmful gases SO2 and CO2. Experiment found that SO2 competes much stronger than CO2 when they co-adsorb in Ni(bdc)(ted)0.5; however, this observation still lacks the physical insights that can be explained through the detailed analyses on the electronic structures obtained from the density functional theory calculations. More details will be presented at the conference.

Keywords: Metal Organic Framework, Carbon Dioxide, Sulfur Dioxide, Electronic Structure, Density Functional Theory

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O2.6

Density-Functional Theory Studies on Activation and Reactions of Light Alkanes over IrO2 (110) Surface

THONG LE MINH PHAM ,1 JYH-CHIANG JIANG2

1Institute of Research and Development, Duy Tan University, 03 Quang Trung, Da Nang, Viet Nam2Department of Chemical Engineering, National Taiwan University of Science and Technology, 43, Keelung

Road, Section 4, Taipei 106, TaiwanEmails: [email protected]

The capability to activate light alkanes at mild temperature and selectively control the oxidation reactions are defined the characteristic of an efficient catalyst for the direct oxidation of light alkanes to value-added products. IrO2 (110) surface, which possesses coordinatively unsaturated iridium and oxygen sites, is expected to be a potential catalyst to activate light alkanes at mild temperature. As a complement for experimental work, theoretical investigation by periodic density functional theory (DFT) calculation with slab model has gradually become the cornerstone for explaining and predicting atomic surface phenomena, such as adsorption, diffusion and chemical reaction. In this work, we employed density functional theory calculations to explore the activation of methane and ethane on the IrO2 (110) surface. The possible reaction pathways of methane and ethane on the IrO2 (110) surface were also investigated. Furthermore, the adsorption characeristics of CHx (x=1-4) and C2H6 on the IrO2 (110) surface were investigated by analysing plots of density of states (DOS) and electron density difference (EDD) contours. Our work has provided an initial basis for understanding and designing efficient catalyst for the direct conversion of methane and ethane to the valuable compounds under mild temperature.

Keywords: methane, ethane, C-H activation, IrO2(110), DFT

References[1] J.J. Siirola, The Impact of Shale Gas in the Chemical Industry, AIChE Journal, 60 (2014) 810-819.[2] Y. Yao, D. Graziano, M. Riddle, J. Cresko, E. Masanet, Greener Pathways For Energy-Intensive Commodity

Chemicals: Opportunities and Challenges, Current Opinion in Chemical Engineering, 6 (2014) 90-98.[3] G. Centi, F. Cavani, F. Trifirò, Selective Oxidation by Heterogeneous Catalysis, Springer US, 2001.[4] Pham, T. L. M.; Leggesse, E. G.; Jiang, J. C., Ethylene Formation by Methane Dehydrogenation and C-C

Coupling Reaction on a Stoichiometric IrO2 (110) Surface - a Density Functional Theory Investigation. Catalysis Science & Technology 2015.

22



O2.7

Colloidal Semiconductor Nanomaterials and Their Optoelectronic Applications

(STEVE) CUONG DANG

Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, The Photonics Institute (TPI),

Nanyang Technological University, 50 Nanyang Ave., 639 798, SingaporeEmail: [email protected]

Colloidal semiconductor nanomaterials are unique material class having wide bandgap tune-ability, stability of inorganic materials and low-cost, flexible manufacture of solution processing materials. Disruptive colloidal quantum dot (QD) technology has found the way from the lab curiosities to the electronic products in shopping centres. In this talk, we will discuss the current state of the art and the future of nanocrystal light emitting devices covering all the intensity levels from quantum light emitters, light emitting diodes (LED) to lasers. At the single particle levels, nanocrystals are artificial atoms and emitting single photons on demand, such long-sought quantum sources are important for quantum technologies and quantum securities. Ensemble nanocrystal films can be processed as active layers following the flexible organic LED architectures to be quantum dot LEDs (QLED) with the stability advantages of inorganic active materials. Because of huge advantages in lighting and display technologies, QLEDs are actively investigated in both academia and industry. Finally, the most advanced light emitting devices (i.e. lasers) are now can be enabled by the most cost-effective technology (i.e. colloidal process) thanks to semiconductor nanocrystals. Unlike current semiconductor lasers which require at least three different technologies and materials to cover the red, green and blue colour, recent breakthroughs in the nanocrystal lasers has promised “long sought” full-colour single-material lasers. Beside these conventional materials, new semiconductor nanocrystals with novel structures such as nanoplatelets, quantum rings are actively investigated from both material theoretical modelling and engineering communities.

23


POSTERS

24


P2.1

A Theoretical Study on Metal Atoms Doped ZnO (1010) Surface for CO Sensing

EN-WEI CHOU, SANTHANAMOORTHI NACHIMUTHU, JYH-CHIANG JIANG *

Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan Email:[email protected]

Carbon monoxide (CO) is one of the most dangerous gases present in indoor and outdoor air. CO is highly toxic gas which is colorless, odorless and difficult to dissolve in water. It is commonly found in the emission of automobile exhausts and the burning of domestic fuels. [1] Hence, in order to maintain the indoor and outdoor air quality and to detect early fires CO sensors are essential. Previously number of different types of CO sensors have been designed. However, developing gas sensors for industrial environments is rather challenging because the sensors must be both highly sensitive and selective. Recently, metal oxides (MOs) have attracted a great attention for gas sensing because of their low-cost, high surface to volume ratios, excellent sensitivity, structural stability, and good mechanical flexibility. [2] Among them, ZnO has been widely investigated for the detection of CO, which can sense CO by means of chemisorption of oxygen with surface and further reaction occurs between adsorbed oxygen and the analyze gas.[3] However, this reaction requires higher temperature. Previously, many efforts have made to reduce the operating temperature, which include doping the metal oxide with noble metals and applying an electrostatic field and found that doping metals on metal oxides is the most favorable. Hence, in this study, we considered the doping of different metal atoms such as Cr (Chromium), Ni (Nickel), Ti (Titanium), and Al (Aluminum) on ZnO and investigated their CO sensing behavior using density functional theory calculations. We have calculated the adsorption energies of CO on different metal atoms doped ZnO surface and also analyzed the electronic properties using density of states (DOS) as in Fig 1, and electron density difference (EDD) contour plots. Our DFT results show that the d orbital of the dopant atoms strongly influences the adsorption of CO on the surface. We found that metal atoms doping increases the adsorption energy of CO compared to pure ZnO surface and among the different metal atoms, Ti atom doping has stronger CO adsorption energy, which is due to the strong interaction between the surface and CO. The interaction between the metal atoms and CO are confirmed by the DOS and EDD plots. Our results confirm that the sensing properties of an oxide material can be modified by means of suitable doping and Ti doped ZnO will be the suitable material to detect CO at room temperature.

Figure 1. Adsorption of CO on Ti doped ZnO(101 0) surface.

Keywords: CO Sensing, Adsorption, Metal Oxides, Density Functional Theory, Doping

References [1] H Gong, J Q Hua, J H Wang, C H Ong and F R Zhu, Sensors Actuators B, 2006, 115, 247–251.[2] Z. Zhang, R. Zou, G. Song, L. Yu, Z. Chen, J. Hu, J. Mater. Chem. 2011, 21, 17360-17365.[3] M Hijiri, L El Mir, S G Leonardi, N Donato and G Neri, Nanomaterials 2013, 3, 357-369.

25


P2.2

Double Carbon-Doped Hexagonal Boron-Nitride as Efficient Metal-Free Catalysts for Oxygen Reduction Reaction:

A Theoretical Study

NGUYEN THI BICH DUYEN, 1 TRAN NGUYEN LAN1,2

1Ho Chi Minh City Institute of Physics, VAST, Ho Chi Minh City, Vietnam2Departments of Physics and Chemistry, University of Michigan, Ann Arbor, MI 48109, USA


Fuel cells have attracted significant attention due to their high efficiency and low pollution. Conventionally, platinum (Pt) and its alloys have been used as catalysts to promote the chemical reactions. However, Pt-based catalysts are expensive and unstable. Therefore, the development of cheap and stable catalysts for oxygen reduction reaction (ORR) is crucial for large-scale commercial applications of fuel cells. Carbon-based catalysts have been extensively investigated [1, 2]. Recently, hexagonal boron-nitride (h-BN) on metal-surface and h-BN/graphene hybrid were shown to be efficient catalysts for ORR [3, 4]. In this study, we theoretically demonstrate that C-doped h-BN can be alternatively used as novel and efficient catalysts for ORR. For theoretical explanation, we used a model of C-doped BN nanoflakes (BNNFs). We found that all reactions can proceed via the four-electron pathway, which is more efficient than the two-electron one. The waters formed are easily released from the system and the initial structure of catalysts is able to recover after finishing OOR as well as ready for the next catalytic process. Different reaction pathways and different doped positions (N or B atoms) were considered. The most importantly, we show that the double C-doped BNNFs are more efficient than single C-doped ones, which have been studied very recently [5, 6]. Our theoretical results are expected to be useful for experiments.

Figure 1. The overall ORR via four-electron reaction pathway (O2 + 4H+ + 4e- 2H2O) using double C-doped BNNFs as catalyst

Keywords: Metal-free catalysts, Boron nitride nanoflakes, Oxygen reduction reaction, Fuel cells

References[1]. L. Zhang and Z. Xia, J. Phys. Chem. C 2010 115, 11170[2]. L. Zhang, J. Niu, L. Dai, and Z. Xia, Langmuir 2012 28 7542 [3]. K. Uosaki, G. Elumalai, H. Noguchi, T. Masuda, A. Lyalin, A. Nakayama, and T. Taketsugu, J. Am. Chem.

Soc. 2014 136 6542[4]. Q. Sun, C. Sun., A. Du, S. Dou, and Z. Li, Nanoscale 2016 8 24084[5]. J. Zhao and Z. Chen, J. Phys. Chem. C 2015 119 26348[6]. M. Gao, M. Adachi, A. Lyalin, and T. Taketsugu, J. Phys. Chem. C 2016 120 15993

26

+4H++4e-

O2

2H2O



P2.3

Capture of Carbon dioxide in Material of Institut Lavoisier-127 by Computational Chemistry Calculations

T. CHOKBUNPIAM, 1 P. PONGSAJANUKUL,2 S. FRITZSCHE,3 S. ASSABUMRUNGRAT,4 S. WONGSAKULPHASATCH,5 T. BOVORNRATANARAKS,6 V. PARASUK2

1Ramkhamhaeng University, Department of Chemistry, Faculty of Science, Bangkok 10240, Thailand2Chulalongkorn University, Computational Chemistry Unit Cell (CCUC), Department of Chemistry, Faculty of

Science, Bangkok 10330, Thailand3University of Leipzig, Institute of Theoretical Physics, Faculty of Physics and Geosciences, Postfach 100920,

D- 04009 Leipzig, Germany4Chulalongkorn University, Center of Excellence in Catalytic Reaction Engineering, Department of Chemical

Engineering, Faculty of Engineering, Bangkok 10330, Thailand5King Mongkut’s University of Technology North Bangkok, Department of Chemical Engineering, Faculty of

Engineering, Bangkok 10800, Thailand6Chulalongkorn University, Department of Physics, Faculty of Science, Bangkok 10330, Thailand


Carbon dioxide (CO2) belongs to the most outstanding air pollutants that cause environment pollution and health risk for human and animals. More important is its emission from industrial processes and from internal combustion engines burning fossil fuels. Therefore, the porous metal organic frameworks namely Material of Institut Lavoisier -127 (MIL-127) was investigated in this work for CO2 capture because of large surface area, high porosity and high thermal stability [1]. The adsorption and diffusion of CO2 in the MIL-127 were studied by Molecular Dynamics (MD) and Gibbs Ensemble Monte Carlo. Several interaction force fields have been calculated and an optimal one has been proposed. The adsorption site of CO2 was found at metal oxide of MIL-127. Moreover, the self diffusion coefficient (around 2-3x10-9 m2/s) increases slightly with increasing concentration while at higher concentrations it declines as a consequence of mutual hindrance of the CO2

molecules.

Figure 1. The structure of MIL-127 in 8 unit cells was constructed from X-Ray crystal data

Keywords: Material of Institut Lavoisier -127 (MIL-127), Carbon dioxide (CO2), Adsorption and diffusion

References [1] Wongsakulphasatch, S.; Nouar, F.; Rodriguez, J.; Scott, L.; Le Guillouzer, C.; Devic, T.; Horcajada, P.;

Greneche, J. M.; Llewellyn, P. L.; Vimont, A.; Clet, G.; Daturi, M.; Serre, C. Direct Accessibility of Mixed-Metal (III/II) Acid Sites through the Green, Scalable and Rational Synthesis of Porous Metal Carboxylates. Chem. Commun. 2015, 51, 10194-10197

27


P2.4

Boron and Nitrogen Doped Graphene as a Counter Electrode for Iodine Reduction in Dye-Sensitized Solar Cells:

A Theoretical Study

KUAN-YU LIN, SANTHANAMOORTHI NACHIMUTHU, JYH-CHIANG JIANG

Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan (R.O.C)

Email:[email protected]

Dye-sensitized solar cells (DSSCs) have attracted extensive attention due to their low cost, high efficiency, and environmentally friendly nature [1]. Finding alternative counter electrodes which can replace expensive, corrosive platinum (Pt) in DSSCs is one of the future avenues for improving DSSC performance and stability at a low cost. Recently, extensive research has been devoted to the development of Pt-free counter electrodes using inorganic metal compounds, conducting polymers, and carbon materials. [2-4] Among them, carbon based materials including carbon nanotubes, and nanocarbon are considered because of their low cost, abundant, and stable in corrosive electrolyte. However, the lower catalytic activity of pristine graphene hinders the practical applications in DSSC electrocatalysts. Conversely, recent studies report that nitrogen-doped graphene could be the efficient electrocatalyst for DSSCs, which improve the electrochemical activity of graphene without significant decrease in conductivity. In order to improve the catalytic activity of graphene further, in this study, we considered doping of both Boron and Nitrogen together and investigated its catalytic activity towards the reduction of Iodine using density functional theory (DFT) calculations. The schematic representation of DSSC components are shown in Figure 1. Among the considered possible adsorption sites, we found that I 2 prefers to adsorb parallel to the boron-nitrogen-doped graphene (BNG) surface. The calculated Iodine anion dissociating barrier in BNG surface (0.41 eV) is much lower than the boron-doped surface, indicating a reduction of Iodine in BNG surface is much faster than boron doped graphene surface. This theoretical study can give a clear understanding of the catalytic mechanism of iodine reduction reaction on BNG surface.

Figure 1: Schematic representation of I2 decomposition on Boron-Nitrogen-doped Graphene (BNG) in DSSCs

Keywords: Dye-sensitized solar cells, Boron-nitrogen-doped graphene, I2 adsorption, iodine reduction, Density functional theory. References[1] Gratzel M, Nature 2001, 414, 338-344.[2] Anghel, B. Marsan B., Cevey Ha N. L., Pootrakulchote N., Zakeeruddin S. M. and Gratzel M., J. Am.

Chem. Soc. 2009, 131, 15976.[3] Tsao, J. Burschka H. N., Yi C. Y., Kessler F., Nazeeruddin M. K. and Gratzel M., Energy Environ. Sci.

2011, 4, 4921.[4] Cai X., Lv Z. B., Wu H. W., Hou S. C. and Zou D. C., J. Mater. Chem. 2012, 22, 9639.

28


P2.5

Multi-Scale Modeling and Simulation of Pyrolysis of Furan

TAM V.-T. MAI, 1 LAM K. HUYNH2

1Molecular Science and Nano-Materials Lab, Institute for Computational Science and Technology, SBI Building, Quang Trung Software City, Tan Chanh Hiep Ward, District 12, Ho Chi Minh City, Vietnam.

2 International University, Vietnam National University – HCMC, Quarter 6, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam.Email: [email protected]

Furan compounds, key products of converting lignocellulosic biomass to biofuels, were recently shown promising alternatives to petroleum-derived fuels. An integrated deterministic and stochastic model, within the master equation/Rice–Ramsperger–Kassel–Marcus (ME/RRKM) framework, was used to characterize the temperature- and pressure-dependent behaviors of pyrolysis of furan – one of the most simple species of furan derivatives – in a wide range of conditions (i.e., 500–2000 K & 0.001–100 atm). Here, using the potential energy surface and molecular properties obtained from high-level quantum chemical methodologies, e.g., CCSD(T)/CBS//UMP2/aug-cc-pVDZ, macroscopic thermodynamic properties, species profiles and phenomenological rate coefficients of the title reaction were satisfactorily derived with the corrections for hindered internal rotation and tunneling treatments. Our calculated/simulated data are in excellent agreement with experimental ones, in which the converging results obtained from both deterministic and stochastic approaches reveal CO + propyne and C2H2 + ketene being of the main decomposition products via two parallel processes, initiated by 1,2-H transfers that result in the formation of cyclic carbene intermediates. Such an agreement and convergence suggest the multi-scale approaches can be confidently used as a post-facto as well as a predicting tool in detailed chemical kinetic modeling/simulation for complex chemical reactions at different T-P conditions served as the optimal process in the internal combustion engines.

Keywords: Furan, Biofuels, Pyrolysis, Kinetic Modeling/Simulation, Rate Constants.

29


P2.6

Detailed Kinetic Mechanism for CH3OO + NO Reaction: A Combined Ab Initio Deterministic and Stochastic Study

NGUYEN T. HOAI, 1,3 TAM V.-T. MAI, LAM K. HUYNH2

1 Institute for Computational Science and Technology, SBI Building, Quang Trung Software City, Tan Chanh Hiep Ward, District 12, Ho Chi Minh City, Vietnam

2 International University, Vietnam National University – HCMC, Quarter 6, LinhTrung Ward, Thu Duc District, Ho Chi Minh City, Vietnam

3 University of Technology, Vietnam National University – HCMC, Ly Thuong Kiet Street, 11 District, Ho Chi Minh City, Vietnam


In this study, the detailed kinetic mechanism of the CH3OO + NO reaction, an important reaction in the NO-to-NO2 conversion relevant to recent NOx-emission control techniques and engine combustion modeling, was intensively investigated using highly-accurate ab initio composite W1U methods (e.g., W1U and CBS-QB3) and statistical Rice-Ramsperger-Kassel-Marcus/Master Equation (RRKM/ME) calculations. Within this framework, the temperature- and pressure-dependent behaviors were intensively characterized using both deterministic and stochastic approaches in a wide range of conditions (T = 298 – 1500 K, P = 7.6 – 76000 Torr). The comparison of the computed thermodynamic results and NIST data shows very good agreement, with differences of approximately 1 kcal/mol or less. The CH3O + NO2 was found to be the most dominant product channel in the considered T-P range, which was found to be in excellent agreement with available kinetic data. The obtained detailed sub-mechanism, consisting of thermodynamic and kinetic data for all species involved and elementary reactions, respectively, can be confidently used for modeling the NO x-emission in the combustion of hydrocarbon fuels.

Keywords: Kinetic mechanism, Peroxy radicals, Nitric oxide, Combustion modeling, Pressure-dependent, Hydrocarbon fuels.

30


P2.7

Low-Temperature Oxidation of Biodiesel Molecules: Rate Rules of Cyclization Reactions from Alkyl-Ester Hydroperoxy Radical

●ROOH

XUAN T. LE, 1, LAM K. HUYNH2

1Institute for Computational Science and Technology at HCMC, Vietnam.2International University, Vietnam National University, HCM, Vietnam.


In this article, the rate rules of cyclization reactions for the hydroperoxy alkyl-ester radical molecules have been conducted for simple surrogates molecules in order to produce the primary characteristics/properties of biodiesel molecules. All of the species were used accurate electronic structure calculations at the CBS-QB3 level of theory combined with statistical mechanics and transition state theory to calculate high-pressure rate constants for selected cyclization reactions, which then serve as the basis to develop rate rules for this type of reactions of alkyl-ester hydroperoxy radicals. The cyclization reactions are believed to be responsible for the formation of cyclic ether and hydroxyl radical in the titled fuel. These rate rules have been developed from a training set of reactions that consist of all C1-C5 ester-alkyl hydroperoxy radical reactants. Our calculations demonstrated the –(C=O)O– ester group in methyl/ethyl esters affect to process that form O–C bond and break O–OH bond, especially at nearest carbon sites of the ester group. These effects can make the reactions occur slower/higher when compared with hydrocarbon fuels. The derived rate rules are recommended to be used to effectively construct detailed kinetic mechanisms for real biodiesel molecules.

Keywords: biodiesel surrogate, alkyl peroxy radical, high-pressure rate rules, low temperature oxidation, cyclization reactions.

31


P2.8

Performance of B3PW91, PBE1PBE and OPBE Functionals in Comparison to B3LYP for 13C NMR Chemical Shift Calculations

NGUYEN THANH SI, PHAM VU NHAT

Department of Chemistry, College of Natural Sciences, Can Tho University, Can Tho, Viet NamEmail: [email protected]

The performance of density functionals B3PW91, PBE1PBE and OPBE are evaluated in comparison to the B3LYP for the 13C NMR chemical shift calculations of 20 small molecules. We combine these functionals with several basis sets including 6-311++G(d,p), 6-311++G(2d,2p), 6-311++G(3df,3pd) and cc-pVTZ to analyze the effect on predicting 13C NMR chemical shifts. Our computed results show that the use of a simple expression δ scal=0.9528 δ calc−0.5986, where δ scal and δ calc are the calculated and the linearly scaled values of the 13C chemical shifts, respectively, significantly improves the mean absolute deviations for a set of 75 chemical shifts considered. In addition the B3PW91 is superior to the other three density functionals and the GIAO B3PW91/6-311++G(2d,2p) is sufficient to determine accurate 13C chemical shifts. The 13C NMR chemical shifts of a larger system, i.e. Taxol molecule, are also computed and compared with experimental values.

B3LYP B3PW91 PBE1PBE OPBE0

2

46

8

10

1214

16

18

0.9977

0.9978

0.99790.998

0.9981

0.9982

0.99830.9984

0.9985

0.9986

Maximum absolute error Mean absolute deviation R-square

Figure 1. Performance of different density functionals in combination with 6-311++G(2d,2p) for 13C NMR chemical shift calculations of 20 small structures in comparison to experimentally observed values.

Keywords: Chemical Shift, Scaling Factor, NMR, DFT, GIAO

32


P2.9

MSMC-GUI: An Interactive Tool for Data Munging and Analysis for Chemical System

TRIET H.M. LE, 1 SON T. DO,1 LAM K. HUYNH2

1Department of Computer Science and Engineering, International University – Vietnam National University,Ho Chi Minh City, Vietnam

2Department of Biotechnology, International University – Vietnam National University, Ho Chi Minh City, Vietnam


Theoretical/computational chemistry has advanced so rapidly that it can serve as a post-facto and predictive tool to study behaviors of various complex chemical/biological systems in a wide range of applications. Specifically, ab initio approaches (i.e., from quantum chemistry to statistical mechanics) have been de-facto tools to estimate reliable thermodynamic data [1] as well as describe kinetic/dynamic behaviors of complex chemical systems [2]. However, such approaches require numerous parameters, which turns out to be still complicated, tedious and sometimes need certain degrees of users’ expertise. Within this framework, we present the Graphical User Interface for our state-of-the-art Multi-Species Multi-Channel program [3] (MSMC-GUI) to facilitate ab initio thermodynamic/kinetic calculations as well as on-the-fly analyses on High-Performance Computing (HPC) platform. Therefore, our tool supports rigorous chemical data pre-/post-processing as well as HPC submission/monitoring in an automatic and comprehensive manner (cf. Figure 1). The robustness of our tool has been demonstrated with a wide range of chemical systems with different complexity. As a result, MSMC-GUI provides the user a reliable and on-the-fly environment to fully exploit any chemical system of interest.

Figure 1. Workflow of MSMC-GUI for reaction data munging and analysis

Keywords: Computational Chemistry, Thermodynamics, Kinetics, Ab initio, High-Performance Computing, Data Analysis, Computer Program

References[1] McQuarrie, D. A., Statistical thermodynamics; Harper and Row: New York, 1973.[2] Steinfeld, J. I., Francisco, J. S.; Hase, W. L., Chemical kinetics and dynamics; Prentice Hall Englewood

Cliffs (New Jersey), 1989; Vol. 3.

33


[3] Duong, M. V., Nguyen, H. T., Truong, N., Le, T. N. M.; Huynh, L. K., Int. J. Chem. Kinet. 2015, 47(9), 564-575.

P2.10

Effects of Metal Substitution in MIL-88A On Hydrogen Adsorption: Computational Study

NGUYEN THI XUAN HUYNH1,2, O MY NA1, DO NGOC SON 1

1Ho Chi Minh City University of Technology, VNU-HCM, Ho Chi Minh City, Vietnam 2Quy Nhon University, Quy Nhon City, Binh Dinh Province, Vietnam


Metal Organic Frameworks (MOFs), a class of porous crystalline materials consisting of metal clusters and organic ligands, is the most promising candidate for many applications such as gas storage and capture, gas mixture separation, and drug delivery. MIL-88A has been evaluated for drug delivery and electrocatalysis but it has not been tested for hydrogen storage. Moreover, we are interested in MIL-88A because of its high stability in the humid environment and hence MIL-88A may be good for a long term usage for hydrogen storage. It was known that creating open metal sites in the MOFs is one of the most effective strategies to enhance the adsorption strength of hydrogen gas with the MOFs [1-3]. This strategy can be applied to MIL-88A by removing counter-anions. In this work, we are concerned with the effects of transition metal substitution in MIL-88A on hydrogen adsorption, which can be clarified by means of the van der Waals dispersion-corrected density functional theory calculations. Furthermore, a quantitative assessment on the hydrogen uptake capacity is also considered through grand canonical Monte Carlo simulations.

Keywords: Hydrogen Adsorption, Metal Organic Framework, Transition Metal, Electronic Structure, Density Functional Theory

AcknowledgementsThis research was funded by Ho Chi Minh City University of Technology under grant number TNCS-2015-KHUD-33.

References[1] T. T. T. Huong, P. N. Thanh, N. T. X. Huynh, and D. N. Son, VNU J. Sci. Math. – Phys. 2016, 32, 1, 67–85.[2] D. a Gomez and G. Sastre, Phys. Chem. Chem. Phys. 2011, 13, 37, 16558–16568.[3] J. L. C. Rowsell and O. M. Yaghi, Angew. Chem. Int. Ed. 2005, 44, 30, 4670–4679.

34



P2.11

Influence of the Hydrogen-Bond Geometry Controlling over Excited State Intramolecular Proton Transfer of 10-Hydroxybenzo[h]quinolone as Fluorescent Probes

WARINTHON CHANSEN, KHANITTHA KERDPOL, RATHAWAT DAENGNGERN, NAWEE KUNGWAN

Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand Email: [email protected]

The excited state intramolecular proton transfer (ESIPT) reactions of 10-hydroxybenzo[h]quinolone (HBQ) and its derivatives with different hydrogen-bonding geometries have been systematically investigated using a hybrid density-functional theory (DFT) and its time-dependent DFT (TD-DFT) at B3LYP with TZVP basis set. ESIPT can occur easily in the excited state with less required PT barrier. On-the-fly dynamics simulations in the first-excited state are employed to determine reaction mechanisms and the time evolution of the ESIPT reaction. The ESIPT times in all compounds take place within 100 fs.

Figure 1. Mechanism of excited state intramolecular proton transfer (ESIPT) for 10-hydroxybenzo[h]quinolone (HBQ).

Keywords: Excited state intramolecular proton transfer, 10-hydroxybenzo[h]quinoline, Density-functional theory, Time-dependent, Dynamics simulations

References [1] Marty L. Martinez, William C. Cooper and Pi-Tai Chou, Chem. Phys. Lett. 1992, 193, 151-154.[2] Bijan Kumar Paul and Nikhil Guchhait, J. Lumin. 2011, 131, 1918-1926.[3] Meng Zhou, Jinfeng Zhao, Yanling Cui, Qianyu Wang, YumeiDai, Peng Song, and Lixin Xia, J. Lumin. 2015, 161, 1-6.[4] Giovanny A. Parada, Todd F. Markle, Starla D. Glover, Leif Hammarstrçm, Sascha Ott, and Burkhard Zietz, Chem. Eur. J. 2015, 21, 6362-6366.

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P2.12

Propane Dehydrogenation on Ni-based catalyst: DFT Study

TINNAKORN SAE-LEE1, ANCHALEE JUNKAEW2, SUPAWADEE NAMUANGRAK2, NAWEE KUNGWAN 1

1 Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand2National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency,

Pathumthani, 12120, Thailand.Email: [email protected]

Propylene, a product from refining petroleum gas, is an important raw material for a variety of products. Production of propylene via propane dehydrogenation (PDH) reaction is an interesting approach because this method can raise a value and expand applications of propane. To date, platinum- (Pt-) and chromium- (Cr-) based catalysts are widely used for PDH. Due to the high reactivity and good stability at high temperatures, nickel-(Ni) based catalysts are one of effective catalysts used in various applications. Ni metal has the lower price than Pt and it is more ecological friendly than Cr. Therefore, Ni is a good candidate for PDH reaction. However, its too high reactivity results in hydrogenolysis process, breaking of C-C bond. This side reaction directly decreases the selectivity of the Ni catalyst. Moreover, deep dehydrogenation reaction, which occurs during desorption of propylene from the surface, leads to a coke formation which is a cause of the catalyst deactivation. In literatures, doping Ni catalyst by gold (Au) can increase the reaction rate of PDH by reducing hydrogenolysis reaction [1,2]. In this work, the insight mechanisms of PDH and other possible side reactions on Ni-based catalysts have been investigated by using DFT calculations implemented in VASP package. As a result, doping Au atoms on Ni surface decreases the adsorption ability of propylene on the catalyst surface but it has no effect on the propane adsorption.

Figure 1. PDH reaction on Ni catalyst

Keywords: “Propylene”, “Ni-based catalyst”, “PDH reaction”, “Hydrogenalysis reaction”, and “Deep dehydrogenation”

References [1] Yan Zhen, Goodman D. Wayne, Catalysis Letters 2012, 142, (5). 517-520.[2] Yan Zhen, Yao Yunxi, Goodman D. Wayne, Catalysis Letters 2012, 142, (6). 714-717.

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P2.13

Substituent Effects on Corrosion Inhibition Performance of Five Natural Thiophene Derivatives: Density Functional Theory and

Molecular Dynamic Simulation Studies

TRUONG DINH HIEU1, DUY QUANG DAO 2,*, THONG LE MINH PHAM2, THI CHINH NGO2, NGUYEN PHAN TRUC XUYEN3, DINH TUAN4, MINH THONG NGUYEN5, PHAM CAM NAM6,*

1Department of Chemistry, Hue University of Education, 34 Le Loi, Hue2Institute of Research and Development, Duy Tan University, 03 Quang Trung, Danang

3Department of Environment and Chemical Engineering, Duy Tan University, 03 Quang Trung, Da Nang4Quality Assurance and Testing Centre 2, 01 Ngo Quyen, Danang

5The University of Danang – Campus in Kon Tum, 704 Phan Dinh Phung, Kon Tum6The University of Danang - Danang University of Science and Technology, 54 Nguyen Luong Bang, Lien

Chieu, DanangEmails: [email protected] (DQD); [email protected](PCN)

Corrosion inhibition performance of five thiophene derivatives extracted from natural products such as 2-Acetylthiophene (AT), 2-Formylthiophene (FT), 2-Methyl-3-thiophenthiol (MTT), 2-Pentylthiophene (PT), 2-Thenylthiol (TT) has been evaluated using Density functional theory (DFT). Quantum chemical parameters characterizing the inhibition activity in gas phase and in aqueous phase were calculated using B3LYP, AFP-D and M05-2X methods combined with 6-311G(d,p) basis set.The obtained results show that the natural thiophene derivatives possess a good inhibition performance. Moreover, it is showed that the thiophene derivatives with electron-releasing substituents like TT, MTT and PT have the better corrosion inhibition activity than those with electron-withdrawing substituents like AT and FT (Figure 1). The corrosion inhibition performance of these studied compounds can be classified in the decreasing trend: TT > MTT > PT > AT > FT. This can be explained by the fact that electron-releasing substituents tend to a higher electron density on thiophene ring and a better adsorption of inhibitors on metal surface, resulting to a higher corrosion inhibition performance.

Figure 1. Optimized structures, HOMO, LUMO and electrostatic potential (ESP) structures of non-protonated form of (a) AT, (b) FT, (c) PT, (d) TT and (e) MTT using APF-D/6-311G(d,p) model chemistry in gas phase.

(ESP structures are displayed at an isovalue of 0.15 and mapped in range from 0.13 to 0.15)

37




Molecular dynamics simulations utilizing Monte Carlo simulated annealing procedure were further applied to simulate the low adsorption configurations of the interaction of the thiophene molecules on the iron surface (Figure 2).

(a) AT-Fe (110) (b) FT-Fe (110) (c) MTT-Fe (110)

(d) PT-Fe (110) (e) TT-Fe (110)

Figure 2. Side views of equilibrium adsorption configurations of (a) AT, (b) FT (c) MTT (d) PT and (e) TT on Fe(110) surface obtained using Monte Carlo simulations in the gas phase

Keywords: Thiophene, Green inhibitor, Iron, Metal corrosion, Natural products, DFT, Monte Carlo

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P2.14

First Principles Calculation of the Hydrogen Adsorption on the Different Pt Surfaces

TRAN THI THU HANH

Computational Physics Laboratory, Ho Chi Minh City University of Technology268 Ly Thuong Kiet, Dist. 10, Ho Chi Minh, Vietnam


The hydrogen adsorption on the Pt(111) and the missing row Pt(110)-(1x2) electrode surfaces has been intensively investigated. To gain insight into detailed atomistic picture on the equilibrium coverage and structure, we have constructed a lattice gas model by determining the on-site energy and the interaction parameters using the first principles total-energy calculation. Therein atop, fcc, hcp and bridge sites for H/Pt(111) and the short bridge on the ridge, the on-top on the micro facet, the hcp and the long bridge sites in the trough for H/Pt(110)-(1x2) are covered by hydrogen atoms under various coverage conditions (0 ML<Θ ≤1 ML) and the total-energy calculations are done for the (1x1), (2x2) and (3x3) cells. The total-energies of (3x3) cell, corrected by the zero-point energy (ZPE), are found well fitted to the lattice gas model. With this model, the Monte Carlo (MC) simulation has been performed. The first-principles calculation combined with MC simulation successfully explains the interaction of H atoms on the Pt surfaces. The active sites of the hydrogen adsorption on the Pt(111) and Pt(110)-(1x2) surfaces, which have been hitherto conceptually discussed but has not been shown by an atomistic simulation, have been identified.

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P2.15

A Theoretical Study on Charge Transport of Dithiolene Nickel Complexes

VU THI THU HUONG , MINH THO NGUYEN

Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001, Leuven, BelgiumEmail: [email protected]

Organic semiconducting materials play an important role in the fabrication of high performance organic electronic devices. In the present work, we theoretically designed a series of organic semiconductors based on nickel complexes. Their characteristics of charge transport were investigated using DFT computational approaches. Based on the computed results, all compounds designed are found to be excellent candidates for ambipolar organic semiconductors with low reorganization energies for both holes and electrons. The (I–V) characteristics and transmission spectra of materials show that the replacement of benzene rings by thiophene rings results in an increase of their HOMO and LUMO energy levels. HOMOs of compounds containing thiophene end-groups are likely dominant for their conductance, while LUMOs of compounds containing benzene end-groups mainly affect their conductance. The electron distribution in these frontier MOs is identified as the main reason which makes the conductance the compounds of in the first series higher than those in the

later series.

40



P2.16

Multiscale Simulations on Conformational Dynamics and Membrane Interactions of the Non-structural 2 (NS2)

Transmembrane Domain

HUYNH MINH HUNG , TRAN DIEU HANG, MINH THO NGUYEN

Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001, Leuven, BelgiumEmail: [email protected]

Hepatitis C virus (HCV) is one of the most crucial global health issues, in which the HCV non-structural protein 2 (NS2), particularly its three transmembrane segments, plays a crucial role in HCV assembly. Multiscale MD simulations have been applied to investigate the preferred orientation of transmembrane domain of NS2 protein (TNS2) in a POPC bilayer, structural stability and characteristic of intramembrane protein-lipid and protein-protein interaction. Residues K27, R32, R43, H45, H47, R61 and K99 have been found to regularly contact with the lipid headgroups. Our study indicates that NS2 protein adopts three trans-membrane segments with highly stable α-helix structure in a POPC bilayer and a short helical luminal segment. While the first and second TM segment involved in continuous helical domain, the third TM segment is however cleaved into two sub-segments with different tilt angles via a kink at L87G88. Salt bridges K81-E45, R32-PO4 and R43-PO4 are determined as the key factor to stabilize the structure of TM2 and TM3 which consist of charged residues located in the hydrophobic region of the membrane.

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P2.17

Free Radical Pathways Lading to the Formation of Nucleobases from Formamide

HUYEN THI NGUYEN , HUYNH MINH HUNG, MINH THO NGUYEN

Department of Chemistry, KU Leuven, B-3001 Leuven, BelgiumEmail: [email protected]

Modelling the complicated chemical reactions in the interstellar media and materials’ surfaces of Titan is nontrivial. Since both the atmosphere and the surface are rich in organic molecules, the relevant chemistry may have important implications for the origin of biomolecules. Prebiotic synthesis of DNA nucleobases from simple molecules such as FM has been known for more than half a century, but the detailed mechanisms are still not clear. In this study, new free radical pathways leading to the synthesis of purine, adenine, guanine, hypoxanthine, xanthine, isoguanine, cytosine, uracil, and thymine were studied at B3LYP/6-311G(d,p) level of theory. The pathways of formation of selected nucleobases demonstrate the importance of free radicals in the production of key biomolecules under conditions appropriate for the interstellar medium or on Titan (low temperatures). The pathways may be universal in nature and proceed without solvent requirements. Our calculations indicate that radical pathways are characterized by smaller energy barriers as compared to previously reported pathways. Overall, these results suggest that the chemistry on Titan's surface and/or the growth of organic particulates in the haze layers in Titan's atmosphere likely involve free radicals. The inherent mechanisms demonstrate that formation of important prebiotic precursors can be predicted. The reaction sequences reported in this study may lead to the production and build-up of molecules with prebiotic relevance.

References[1] Jeilani, Y.A., Nguyen, H.T., Newallo, D., Dimandja, J.-M.D., and Nguyen, M.T., Phys. Chem. Chem. Phys.

15 (2013) 21084-21093.[2] Jeilani, Y.A., Nguyen, H.T., Cardelino, B.H., and Nguyen, M.T., Chem. Phys. Lett. 598 (2014) 58-64.[3] Nguyen, H. T, Jeilani, Y. A., Hung, M. H., and Nguyen, M. T., J. Phys. Chem. A 119 (2015) 8871-8883.

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P2.18

Catalytic Effects of Small Pure and Earth-Alkali Mixed Silicon Clusters Sim-nMn (m = 3 – 4, n = 0 – 1) with M = Be, Mg, Ca

towards the Methanol Activation

TRAN DIEU HANG , MINH THO NGUYEN

Department of Chemistry, KU Leuven, BelgiumEmail: [email protected]

The methanol activation pathways occurring on small pure and mixed silicon clusters Sim-nMn with M = Be, Mg, Ca, and m = 3 – 4, n = 0 – 1 were investigated using quantum chemical computations (density functional theory B3LYP/aug-cc-pVTZ and coupled-cluster theory CCSD(T)/CBS extrapolated from energies with the aug-cc-pVnZ basis sets) to examine their thermodynamic and kinetic feasibilities. In all cases considered, the cleavage of the O–H bond is favored over that of the C–H bond. The O–H bond cleavage in the presence of the singlet Si 3

cluster is less thermodynamically preferred than on mixed Si2M clusters, even though it becomes more kinetically favored. Replacement of one Si atom in the Si4 cluster with earth-alkaline metals substantially reduces the energy barriers for both O–H and C–H dissociation paths. The most energetically preferred pathway for breaking the O–H bond takes place on the Si3Ca cluster with a small energy barrier of only 2 kcal/mol. Most importantly, the energy barriers for the O–H bond breaking on the singlet Si3, Si2Ca and Si3Ca clusters are found to be lower than the previously reported results for metal clusters, catalytic metal surfaces, metal oxides…The small mixed Si clusters thus appear to be good catalysts for methanol activation, and most probably in other dehydrogenation processes from the X-H bonds of organic compounds. These findings suggest a further extensive search for doped silicon clusters as realistic catalysts that can experimentally be prepared, for methanol activation particularly and dehydrogenation processes generally.

Figure 1: Schematic potential energy profile illustrating the methanol dissociation reaction of methanol in the presence of the singlet Si3Ca cluster. Relative energies in kcal/mol were obtained from CCSD(T)/CBS + ZPE computations.

References[1] Hang, T. D.; Hung, H. M.; Nguyen, H. T.; Nguyen, M. T. Structures, Thermochemical Properties, and

Bonding of Mixed Alkaline-Earth-Metal Silicon Trimers Si3M +/0/– with M = Be, Mg, Ca. J. Phys. Chem. A 2015, 119, 6493–6503.

[2] Hang, T. D, ; Nguyen, H. T. ; Nguyen, M. T. Methanol Activation Catalyzed by Small Earth-Alkali Mixed Silicon Clusters Sim-nMn with M = Be, Mg, Ca and m = 3 – 4, n = 0 – 1. J. Phys. Chem. C, 2016, 120, 10442–10451.

43



P2.19

Photoinduced Proton Transfer of 7-Hydroxyquinoline via Intermolecular Hydrogen-Bonded Wire of Mixed Methanol and

Water: Theoretical Insights

K. KERDPOL1, R. DAENGNGERN1,2, J. MEEPRASERT2, S. NAMUANGRUK2, N. KUNGWAN 1

1Department of Chemistry, Faculty of Science, Chiang Mai University, 50200 Chiang Mai, Thailand2National Nanotechnology Center (NANOTEC), NSTDA, 111 Thailand Science Park, Pahonyothin Road,

Klong Luang, 12120 Pathum Thani, ThailandEmail: [email protected]

Intermolecular multiple proton transfer (PT) reactions of 7-hydroxyquinoline (7HQ) with mixed methanol and water clusters, [7HQ(X)3 when X = M-methanol and W-water] (Fig. 1), both in ground (S0) and first excited (S1) states have been studied by using density functional theory (DFT) at B3LYP and its time-dependent DFT with 6-31+G(d,p) basis set. For all complexes, the intermolecular hydrogen bonds involving PT process are strengthened in the S1 state, confirmed by the short intermolecular hydrogen-bonded distances and the red-shift of the O–H stretching vibrational frequencies especially the O–H proton donor of 7HQ. Therefore, PT may occur firstly via the breaking O–H bond of 7HQ. Furthermore, the potential energy curves both in S0 and S1

states were calculated to investigate the effect of different solvents surrounding 7HQ. PT reactions can occur easily in the S1 state due to the low PT energy barrier. For pure solvent, the excited-stated proton transfer (ESPT) is likely to occur better in methanol (4.22 kcal/mol) than water (6.67 kcal/mol). For mixed solvent, the ESPT energy barriers increase gradually when replacing methanol with one up to three water molecules thus water may block ESPT reaction.

Figure 1. Scheme of (a) isolated 7-hydroxyquinoline (7HQ) and (b) 7HQ with a solvent wire (methanol and water)

Keywords: “7-Hydroxyquinoline (7HQ)”, “Excited-Stated Proton Transfer (ESPT)”, “Mixed Methanol-Water”, “B3LYP”, “Solvent Effect”

References[1] K. Kerdpol, R. Daengngern, J. Meeprasert, S. Namuangruk, N. Kungwan, Theor. Chem. Acc., 2016, 135,

(208), 1-9.[2] Y. Matsumoto, T. Ebata, N. Mikami, J. Phys. Chem. A., 2002, 106, (23), 5591-5599.[3] Y. Cui, H. Zhao, J. Zhao, P. Li, P. Song, L. Xia, New. J. Chem., 2015, 39, 9910-9917.

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P2.20

A DFT Study on Antioxidant Activity of Oxygenated Terpenoids Extracted from Cleistocalyx operculatus

THI CHINH NGO1, DUY QUANG DAO 1, PHAM CAM NAM2

1Institute of Research and Development, Duy Tan University, 03 Quang Trung, Danang, Viet Nam2Department of Chemistry, Danang University of Science and Technology - The University of Danang, 54

Nguyen Luong Bang, Lien Chieu, Danang, Viet Nam


Antioxidant capacity of 21 oxygenated monoterpenes and desquiterpenes extracted from buds of Cleistocalyx operculatus [1] has been investigated in this study using density functional theory (Figure 1). Insight into the theoretical mechanism of antioxidant activity of these compounds was clarified via three antioxidant mechanisms including hydrogen atom transfer (HAT), single electron transfer followed by-proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET). The various calculated thermochemical parameters were performed using density functional theory (DFT) method at (RO)B3LYP/6-311++G(2df,2p)//B3LYP/6-311G(d,p) level of theory in the gas phase, ethanol and water.As a result, falcarinol is the most effective antioxidant via both HAT and SPLET mechanisms. In fact, the BDE in the gas phase of falcarinol is 66.5 kcal/mol which is much lower than the one of phenol. The presence of both OH group and unsaturated double/triple bonds supports this molecule to have the good antioxidant properties.

Figure 1. Chemical structure of 21 oxygenated monoterpenes and desquiterpenes

45



Keywords: Antioxidant, BDE, IE, HAT, SET-PT, SPLET, Natural compounds, Density functional theory.

References

[1] Ngo, T. C.; Dao, D. Q.; Thong, N. M.; Nam, P. C., Insight into the antioxidant properties of non-phenolic terpenoids contained in essential oils extracted from the buds of Cleistocalyx operculatus: a DFT study. RSC Advances 2016, 6, 30824-30834

[2] NIST Chemistry WebBook. http://webbook.nist.gov/chemistry/ 2015.

46


P2.21

Etherification Mechanism of DMDHEU with Primary Alcohols in Acidic Condition Studied with ab initio Quantum Chemistry

Methods

NGUYEN THUONG DANG , PHAM THANH QUAN, PHAM HONG PHUOC SANG

Faculty of Chemical Engineering – University of Technology – Vietnam National University, HCMCEmails: [email protected] (NTD); [email protected] (PHPS)

This paper establishes the etherification mechanism of 4,5-dihydroxy-1,3-bis (hydroxymethyl) imidazolidin-2-one (DMDHEU) with primary alcohols R-CH2OH in acidic condition using density functional theory B3LYP, through surveying the effect of the substituent –R (R = H, CH3, CH2CH3, Vinyl, CH2NHCH3, CH2OCH3, CH2Cl, MDHEU) and the effect of basis set (6-31g(d,p), 6-311g(d,p), 6-311++g(d,p)) on computational results. The results indicate that the etherification reaction follows nucleophilic substitution unimolecular (S N1) mechanism. Reactants and products form reactive intermediates with H+ and water, in this state H+ is occupied by both alcohol and water or ether and water. This state has lower energy level compared to both of the following cases: H+ is occupied only by water; and H+ is occupied only by the product/reactant. The substituent –R has a significant impact on the amount of energy needed to convert the reactive intermediate into ether but shows no effect on activation energy; while the basic set affects both activation energy and conversion energy.

Keywords: Etherification Reaction Mechanism, DMDHEU, Primary Alcohol, Effect of H+.

47




P2.22

Tiny Clusters Containing Transition Metals: Electronic Structures and Insights into Their Anion Photoelectron Spectra

LE NHAN PHAM, 1,2 MINH THO NGUYEN1

1Department of Chemistry, KU Leuven Belgium2Department of Chemistry, University of Dalat, Lam Dong Vietnam


Theoretical studies on clusters containing transition metals are one of the interesting and challenging topics. The main reason is electronic structures of these systems need to be described with appropriate wavefunctions. Usually, single reference wavefunctions can describes the electronic structure of many systems. For several systems, single reference wavefunctions cannot be used efficiently with regards to correlation energy. In such situations, multireference wavefunctions are believed to be an alternative. Therefore, in this work, we utilize single reference and multireference quantum wavefunction types (DFT, RCCSD(T), CASSCF, MRCI, CASPT2 and NEVPT2) to synergistically investigate the electronic structures of tiny clusters containing transition metals (VC2-/0, ScSi2-/0 and TiGe2-/0). On the basis of their electronic structures, possible one-electron ionization processes, which are the removals of one electron from anionic clusters, are predicted. These ionization energies, the so-called adiabatic and vertical detachment energy (ADE and VDE), are also calculated at several levels of theory mentioned above. These calculated ADEs and VDEs provide reliable evidences to understand nature of all experimental photoelectron bands in the spectra. In addition, multidimensional Franck-Condon simulations can be employed to confirm electronic transitions and/or provide more details about experimental results.

Keyword: Clusters, transition metals, anion, photoelectron, excited state, ground state

48


P2.23

Solvent Control of Molecular Structure and Excited-State Proton Transfer Process : Dynamics Simulations of 2-(2’-hydroxyphenyl) Benzimidazole (HBI)

CHANATKRAN PROMMIN , KHANITTHA KERDPOL , RATHAWAT DAENGNGERN, NAWEE KUNGWAN

Department of Chemistry, Faculty of Science, Chiang Mai University,Chiang Mai 50200, Thailand


The excite-state intramolecular proton transfer (ESIPT) is one the most fundamental and important process due to its photophysical properties. The applications of ESIPT are found in many applications such as organic light emitting diodes, luminescent materials and fluorescent probes. As in fluorescent probes, one of the most widely use dye is 2-(2'-hydroxyphenyl) benzimidazole (HBI). In this study, static calculations and dynamics simulations of the excited-state proton transfer (ESPT) for HBI in several types of solvents were systematically examined by density funcational theory (DFT) at B3LYP/6-31G method. In various kinds of isomers of HBI, ESPT can occur both in the ground and excited state. It has also been recognized that this proton transfer is a very fast reaction and the phototautomer is formed during the lifetime of the originally excited species. This may lead to a change in physical or chemical properties of the molecule, which dictates its optical properties as fluorescent probe. Our calculated results can explain the phenomena found in the experimental study in term of the weak sovolchromism when protic solvents form an intermolecular hydrogen-bond with HBI

Figure 1. Principal photophysics of ESIPT Illustrated by 2-(2-hydroxyphenyl)-benzimidazole (HBI)

Keywords: : 2-(2'-hydroxyphenyl)benzimidazole (HBI), Excite-state intramolecular proton transfer (ESIntraPT), Excite-state intermolecular proton transfer (ESInterPT), Density funcational theory

References[1] R. Hossein, M. Nafiseh, and H. Fahemeh, Chem. Phys. 2014, 444, 66-76.[2] R. Hossein, M. Nafiseh, and H. Fahemeh, Spectrochim. Acta A, 2014, 118, 228-238.[3] D. Rathawat, and K. Nawee, Chem. Phys. Lett. 2014, 609, 147-154.

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P2.24

Dynamic Simulations on Hydrogen Bonding in the Excited State of 3-hydroxyflavones and its Solvent Assistance

RUSRINA SALAEH , KHANITTHA KERDPOL, RATHAWAT DAENGNGERN, NAWEE KUNGWAN

Department of Chemistry, Faculty of Science, Chiang Mai University,Chiang Mai 50200, ThailandEmail: [email protected]

3-Hydroxyflavone (3HF) is composed of phenyl and pyranyl ring. This molecule belongs to a group of flavonoids, which are responsible for the yellow color of petals. The photophysical change affected by intermolecular hydrogen-bonded with protic solvent is very important information in the molecular level of this molecule to be used as effective fluorescent probes for ions. In this work, the possible excited-state intra- and intermolecular proton transfer (ESPT) reactions of 3HF in methanol, water, and ammonia have been theoretically studied both static and dynamic calculations using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. An analysis of the absorption and emission spectra as well as the time constant of proton transfer was used to explain the optical changed with different solvents. The results demonstrate that the enol and keto forms of 3HF can exist when a protic solvent is introduced. Both excited-state intra- and intermolecular proton transfers can be competitive when increasing the polarity of solvent, resulting in slower proton transfers.

Figure 1. Tautomerization of 3-hydroxyflavone (3HF) and 3-hydroxyflavone with solvent.

Keywords: 3-hydroxyflavone, intra- and intermolecular excited-state proton transfe, protic solvent, density functional theory (DFT), time-dependent DFT (TD-DFT)

References [1] Gunduz, S.; Goren, C. A.; and Ozturk, T, Org. Lett 2012, 14, 1476-1579.[2] Sengupta, K. P.; Kasha, M, Org. Lett 1979, 68, 382.[3] Klymchenko, S. A.; Demchenko, P. A., New. J. Chem 2004, 28, 687-692.[4] Douhal, A.; Sanz, M.; Tormo L.; Organero A. J., Chem Phys Chem 2005, 6, 419-429.

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P2.25

The Effect of Co/Ni-Promoted on Edge Site of MoS2 Catalyst for H2 Activation Mechanism using a Periodic DFT Study

CHANCHAI SATTAYANON,1 SUPAWADEE NAMUANGRUK,2 NAWEE KUNGWAN,1

MANASCHAI KUNASETH 2

1Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai , 50200, Thailand2National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency

(NSTDA), Pathum Thani, 12120, Thailand Emails: [email protected] (NK); [email protected] (MK)

Understanding the mechanism of molecular hydrogen (H2) activation on MoS-based catalysts is very important for hydrotreating processes, which are crucial for hydrodesulfurization (HDS) and hydrodeoxygenation (HDO) reactions. In this work, three major mechanisms of H2 activation (adsorption, dissociation and diffusion) on NiMoS and CoMoS catalysts under HDS/HDO conditions were investigated by means of density functional theory calculations. The results ofH2 adsorption on NiMoS and CoMoS catalysts revealed that H2 molecule preferred to be adsorbed on metal atoms rather than the sulfide group, while the H 2 molecule adsorbed on CoMoS surface but substantially weaker on NiMoS surface. In addition, the transition state calculation using improved nudged-elastic band method indicated that the energy barrier of H2 dissociation on NiMoS is lower than that of CoMoS, while diffusion of dissociated hydrogen atoms on the surfaces of both catalysts occurred easily. In conclusion, the high temperature and high pressure of H2 feedstock of HDS/HDO conditions are adequate for H2 dissociation and diffusion on NiMoS and CoMoS.

Figure 1. Overview of H2 activation on both CoMoS and NiMoS catalysts

Keywords: Hydrogen adsorption, Hydrogen dissociation, NiMoS, CoMoS, Density functional theory

References[1] Badawi, M.; Cristol, S.; Paul, J.-F.; Payen, E. Comptes Rendus Chimie 2009, 12, 754.[2]Badawi, M.; Paul, J. F.; Payen, E.; Romero, Y.; Richard, F.; Brunet, S.; Popov, A.; Kondratieva, E.; Gilson,

J. P.; Mariey, L.; Travert, A.; Maugé, F. Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles 2013, 68, 829.[3] Ruinart de Brimont, M.; Dupont, C.; Daudin, A.; Geantet, C.; Raybaud, P. Journal of Catalysis 2012, 286,

153.[4] Zhang, H.; Lin, H.; Zheng, Y. Applied Catalysis B: Environmental 2014, 160–161, 415.[5] Prodhomme, P.-Y.; Raybaud, P.; Toulhoat, H. Journal of Catalysis 2011, 280, 178.

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P2.26

Structure, Thermochemical Properties and Growth Sequence of Aluminum Doped Silicon Clusters SinAlm (n = 1 – 11, m = 1 – 2)

and Their Anions

NGUYEN MINH TAM , MINH THO NGUYEN

1 Research Group of Computational Chemistry, Ton Duc Thang University, Vietnam


A systematic examination of the aluminum doped silicon clusters, SinAlm with n = 1 – 11 and m = 1 – 2, in both neutral and anionic states, is carried out using quantum chemical calculations. Lowest-energy equilibrium structures of the clusters considered are identified on the basis of G4 energies. High accuracy total atomization energies and thermochemical properties are determined for the first time using the G4 and CCSD(T)/CBS (coupled-cluster theory with complete basis set up to n = 3) methods. In each size, substitution of Si atoms at different positions of a corresponding pure silicon clusters by Al dopants invariably leads to a spectrum of distinct binary structures but having similar shape and comparable energy content. Such an energetic degeneracy persists in the larger cluster sizes, in particular for the anions. The equilibrium growth sequences for Al-doped Si clusters emerge as follows: i) neutral singly doped SinAl clusters favor Al atom substitution into a Si position in the structure of the corresponding cation Sin+1

+, whereas the anionic SinAl- has one Si atom of the isoelectronic neutral Sin+1 being substituted by the Al impurity, and ii) for doubly doped SinAl2

0/- clusters, the neutrals have the shape of Sin+1 counterparts in which one Al atom substitutes a Si atom and the other Al adds on an edge or a face of it, whereas the anions have both Al atoms substitute two Si atoms in the Sin+2

+ frameworks. The higher stability of the closed shell Si9Al- can be rationalized in terms of the jellium electron shell model.

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P2.27

Structure, Magnetism, and Dissociation Energy of Small Bimetallic Cobalt-Chromium Oxide Cluster Cations

NGUYEN MINH TAM, 1,2 HUNG TAN PHAM,3 NGO TUAN CUONG,4 NGUYEN THANH TUNG5

1 Research Group of Computational Chemistry, Ton Duc Thang University, Ho Chi Minh City, Vietnam2 Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam

3 Institute for Computational Science and Technology, Viet Nam4 Center for Computational Science, Hanoi National University of Education, Viet Nam5 Institute of Materials Science, Vietnam Academy of Science and Technology, Viet Nam


The cationic clusters CoxCryO+m(x + y = 2, 3 and 1 ≤ m ≤ 4) are investigated using combined experimental

photodissociation mass spectrometry and density functional theory calculations. It is found that the clusters grow preferentially through maximizing the number of metal–oxygen bonds with a favor on Cr sites. The size- and composition-dependent magnetic behavior is discussed in relation with the local atomic magnetic moments. While doped species show an oscillatory magnetic behavior, the total magnetic moment of pure cobalt and chromium oxide clusters tends to enhance or reduce as increasing the oxygen content, respectively. The dissociation energies for different evaporation channels are also calculated and compared with the experimental observations as well as to suggest the stable patterns, as fingerprints for future photofragmentation experiments.

References[1] Nguyen Thanh Tung, Nguyen Minh Tam, Minh Tho Nguyen, Ewald Janssens, Peter Lievens; Journal of

Chemical Physics, Vol. 141, 2014, 04431-04437.[2] Hung Tan Pham, Ngo Tuan Cuong, Nguyen Minh Tam, Vu Dinh Lam, Nguyen Thanh Tung; Chemical

Physics Letters, Vol. 643, 2016, 77-83.

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P2.28

Theoretical Study of Small Scandium-Doped Silver Clusters ScAgn with n= 1–7: σ-Aromatic Feature

LOC QUANG NGO , HUNG TAN PHAM, PHUONG MY HO-PHAM, MINH THO NGUYEN

Institute of Computational Science and Technology, Ho Chi Minh City, Viet NamEmail: [email protected]

In this theoretical investigation, the geometry, chemical bonding and aromatic feature of silver cluster doped by Sc are explored by the mean of DFT calculation. The planar shape is found for all ScAg n clusters. The growth mechanism is illustrated as formation of the hexagonal and heptagonal metal cycles by increasing the number of Ag atoms. Particularly, the ScAg6

- and ScAg7 present the planar metal cyclic form in which Sc atom locates at the central position of Ag6 and Ag7 cycles. The σ aromaticity is demonstrated by exist of strongly diatropic current for both ScAg6

-, ScAg7 and ScCu7 clusters. In Sc doped ScAgn clusters, the delocalized bonding pattern is found as a connector between Sc and Agn host, as indicated by ELI_D analysis.

References

[1] H. T. Pham, L. Q. Ngo, M. P. Ho-Pham, M. T. Nguyen, J. Phys. Chem. A, 2016, 120, 7964–7972.

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P2.29

Mechanism of the Oxidation Process of 1,2-Naphthoquinone by Hydroxyl Radicals in Water Studied using a DFT Approach

NGÔ QUANG LỘC ,1 PHẠM HỒ MỸ PHƯƠNG1,2

1Institute for Computational Science and Technology, Ho-Chi-Minh City (ICST), Vietnam2 Faculty of Chemical Engineering, Ho Chi Minh City University of Technology (HCMUT), Vietnam


The decomposition mechanism of 1,2-naphthoquinone in the presence of hydroxyl radicals and oxygen was investigated by using DFT approach coupled with 6-311++G(d,p) basis set. The intermediates and transition state as well as the energy profile for each reaction were discovered and calculated. Our results suggest that ring-open and oxidization products such as: 2-formyl-Benzoic acid, catechol, benzene-1,2,3-triol, maleinaldehydic acid, and a few oxo acids along with water and carbon dioxide are formed. A reaction coordinate for each major product is then plotted to illustrate the changes in energy in the system. It is shown that most reactions are exothermic and require low to mild input energy to overcome the classical barrier.

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P2.30

Effects of (-)-epigallocatechin-3-gallate (EGCG) on the Oligomerization of Amyloid Beta (16-22) Hexamer: A Theoretical

Study

SON TUNG NGO, 1,2 DUC TOAN TRUONG,3 NGUYEN MINH TAM1,2

1Computational Chemistry Research Group, Ton Duc Thang University, Ho Chi Minh City2Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam

3Department of Theoretical Physics, University of Sciences, Ho Chi Minh City, Vietnam Email: [email protected]

The (-)-epigallocatechin-3-gallate (EGCG), a small compound deriving from green tea, consists of the aromatic rings that can form π-π stacking interactions with the amyloid beta (Aβ) residues able to prevent the formation of Aβ oligomers. An extensive replica exchange molecular dynamics simulation was performed to investigate the physical insight of the inhibition of EGCG on the Aβ16-22 hexamer. The changes in the structure of oligomers when EGCG is present and absent were monitored and analyzed. REMD results indicate that EGCG not only reduces the β-content of the oligomer over all considered snapshots, but also it decreases the β-sheet sizes with an order of higher than two of the oligomers that correspond to the highly neurotoxic forms. Moreover, EGCG has the possibility to accelerate the oligomerization process of the Aβ peptide, thus reduces the number of toxic conformations of Aβ oligomer. The investigated inhibitor is bound to the peptide with the same level to curcumin, but in a different scheme that EGCG creates strong electrostatic interactions to the receptor. The appearance of EGCG tends to decrease the binding free energy between constituting monomers to the others of the Aβ16-22 hexamer. In addition, the π-π stacking is indicated to be a critical factor of the non-bonded interaction between EGCG and the peptide, which was investigated using quantum chemical methods (density functional theory with the B97-D functional and the 6-311++G(d,p) basis set).

56



P2.31

Electronic Structure and Thermochemical Parameters of the Silicon-Doped Boron Clusters BnSi, with n = 8–14, and Their

Anions

LONG VAN DUONG, 1 DANG THI TUYET MAI,2 MINH THO NGUYEN2

1 Institute for Computational Science and Technology (ICST), Quang Trung Software City, Ho Chi Minh City, Viet Nam

2 Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, BelgiumEmail: [email protected]

We performed a systematic investigation on silicon-doped boron clusters BnSi (n = 8–14) in both neutral and anionic states using quantum chemical methods. Thermochemical properties of the lowest-lying isomers of BnSi0/– clusters such as total atomization energies, heats of formation at 0 and 298 K, average binding energies, dissociation energies, etc. were evaluated by using the composite G4 method. The growth pattern for B nSi0/–

with n = 8–14 is established as follows: (i) BnSi0/– clusters tend to be constructed by substituting B atom by Si-atom or adding one Si-impurity into the parent Bn clusters with n to be even number, and (ii) Si favors an external position of the Bn frameworks. Our theoretical results reveal that B8Si, B9Si–, B10Si and B13Si– are systems with enhanced stability due to having high average binding energies, second-order difference in energies and dissociation energies. Especially, by analyzing the MOs, ELF, and ring current maps, the enhanced stability of B8Si can be rationalized in terms of a triple aromaticity.

Keywords: Boron Clusters, Silicon-doped, Aromaticity, Ring Current

57



P2.32

Aromatic Character of Planar Boron-based Clusters Revisited by Ring Current Calculations

HUNG TAN PHAM ,1 MINH THO NGUYEN2

1Institute of Computational Science and Technology, Ho Chi Minh City, Viet Nam2Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium


The planarity of small boron-based clusters is the result of an interplay between geometry, electron delocalization, covalent bonding and stability. These compounds contain two different bonding patterns involving both σ and π delocalized bonds, and up to now, their aromaticity has been assigned mainly using the classical (4N + 2) electron count for both types of electrons. In the present study, we reexplored the aromatic feature of different types of planar boron-based clusters making use of the ring current approach. The B3

+/-, B42-,

B5+/-, B6, B7

-, B82-, B9

-, B102-, B11

-, B12, B13+, B14

2- and B162- are characterized by magnetic responses to be doubly σ

and π aromatic species in which the π aromaticity can be predicted using the (4N + 2) electron count. The triply aromatic character of B12 and B13

+ is confirmed. The π electrons of B182-, B19

- and B202- obey the disk aromaticity

rule with electronic configuration of [1σ21π41δ42σ2] rather than the (4N + 2) count. The double aromaticity feature is observed for boron hydride cycles including B@B5H5

+, Li7B5H5 and M@BnHnq clusters from both the

(4N + 2) rule and ring current maps. The double π and σ aromaticity in carbon-boron planar cycles B 7C-, B8C, B6C2, B9C-, B8C2 and B7C3

- is in conflict with the Huckel electron count. This is also the case for theions B11C5+/-

whose ring current indicators suggest that they belong to the class of double aromaticity, in which the π electrons obey the disk aromaticity characteristics. In many clusters, the classical electron count cannot be applied, and the magnetic responses of the electron density expressed in terms of the ring current provide us with a more consistent criterion for determining their aromatic character.

References

[1] H. T. Pham, K. Z. Lim, R. W. A. Havenith, M. T. Nguyen, Phys. Chem. Chem. Phys., 2016, 18, 11919-11931.

58


P2.33

Mn2@Si15: the Smallest Triple Ring Tubular Silicon Cluster

HUNG TAN PHAM ,1 LONG VAN DUONG,1 NGUYEN MINH TAM,1 MINH THO NGUYEN2

1Institute of Computational Science and Technology (ICST), Ho Chi Minh City, Viet Nam2Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium


The smallest triple ring tubular silicon cluster Mn2@Si15 is reported for the first time. Theoretical structural identification shows that the Mn2@Si15 tubular structure whose triple ring is composed by three five-membered Si rings in anti-prism motif, is stable in high symmetry (D5h) and singlet ground state (1A1’). The dimer Mn2 is placed inside the tubular along the C5 axis, and the Mn dopant form single Si–Mn bonds with Si skeleton, whereas the Mn–Mn is characterized as a triple bond. The effect of Mn2 on the stability of the Si15 triple ring structure arises from strong orbital overlap of Mn2 with Si15.

Reference[1] H. T. Pham, T. T. Phan, N. M. Tam, D. V. Long, M. T. Nguyen, Phys. Chem. Chem. Phys., 2015, 17, 7566.

59



P2.34

Effects of Bimetallic Doping on Small Cyclic and Tubular Boron Clusters: B7M2 and B14M2 Structures with M = Fe,Co

HUNG TAN PHAM ,1 MINH THO NGUYEN2

1Institute of Computational Science and Technology, Ho Chi Minh City, Viet Nam2Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium


Using density functional theory with the TPSSh functional and the 6-311+G(d) basis set, we extensively searched for the global minima of two metallic atoms doped boron clusters B 6M2, B7M2, B12M2 and B14M2 with transition metal element M being Co and Fe. Structural identifications reveal that B7Co2, B7Fe2 and B7CoFe clusters have global minima in a B-cyclic motif, in which a perfectly planar B7 is coordinated with two metallic atoms placed along the C7 axis. The B6 cluster is too small to form a cycle with the presence of two metals. Similarly, the B12 cluster is not large enough to stabilize the metallic dimer within a double ring 2xB6 tube. The doped B14M2 clusters including B14Co2, B14Fe2 and B14CoFe have a double ring 2 x B7 tubular shape in which one metal atom is encapsulated by the B14 tube and the other is located at an exposed position. Dissociation energies demonstrate that while bimetallic cyclic cluster B7M2 prefers a fragmentation channel that generates the B7 global minimum plus metallic dimer, the tubular structure B14M2 tends to dissociate giving a bimetallic cyclic structure B7M2 and a B@B6 cluster. The enhanced stability of the bimetallic doped boron clusters considered can be understood from the stabilizing interactions between the anti-bonding MOs of metal–metal dimers and the levels of a disk aromatic configuration (for bimetallic cyclic structures), or the eigenstates of the B 14 tubular form (in case of bimetallic tubular structure).

Reference [1] H. T. Pham, M. T. Nguyen, Phys. Chem. Chem. Phys., 2015, 17, 17335.

60


P2.35

Ab initio Chemical Mechanisms of SiHx+

(x = 1-3) Ions Reactions with SiH4

TRONG NGHIA NGUYEN, 1,2 M. C. LIN1

1 Center for Interdisciplinary Molecular Science, Department of Applied Chemistry, National Chiao Tung University, Hsinchu 300, Taiwan. E-mail: M. C. Lin, [email protected]

2 Department of Physical Chemistry, Hanoi University of Science and Technology, No. 1, Dai Co Viet, Ha Noi, Viet Nam.


The mechanisms for reactions of SiH4 and SiHx+ (x = 1,2,3) ions, which are known to coexist under CVD

conditions, have been investigated by high level ab initio electronic structure calculations based on the CCSD(T)/CBS//B3LYP/6-311++G(3df,2p), CCSD(T)/CBS//CCSD/6-311++G(3df,2p), and CCSD(T)/CBS//CCSD(T)/6-311++G(d,p) methods. For the barrierless radical association processes, their variational transition states have been characterized by the CASPT2//CASSCF method. Our results show that SiH3

+ ion mainly abstracts one of the H atoms in SiH4, while SiH+ and SiH2+ ions can both abstract the H or

insert into one of the Si-H bonds of SiH4. The abstraction reactions of SiHx+ (x = 1-3) ions with SiH4 occur by

initial association via complexes LM6 (HSi-H2SiH2+) , LM3 (H2Si-HSiH3

+), and LM1 (H3Si-HSiH3+) with 33.4,

36.2, and 35.6 kcal/mol bind energies to be followed by fragmentation giving SiH 2+ + SiH3 (41.9 kcal/mol),

SiH3+ + SiH3 (-1.2 kcal/mol), and SiH4 + SiH3

+ (0.0 kcal/mol), respectively. The insertion reactions of SiH+ and SiH2

+ ions with SiH4 occur via long-live intermediates, H2SiSiH3+ (-47.4 kcal/mol) and H3SiSiH3

+ (-40.9 kcal/mol), respectively, which can fragment to various smaller species as depicted by the PESs. The major products of the reactions are Si2H3

+ + H2; SiH3+ + SiH3 and H3SiSiH+ + H2; and SiH4 + SiH3

+, respectively. The predicted results by the different methods are close to one another; the predicted structural parameters and enthalpy changes agree well with available data.

61


Figure 1. Potential energy diagrams for the SiH+ and SiH2+ + SiH4 reactions computed at the

CCSD(T)/CBS//B3LYP/6-311++g(3df,2p) level. The values in the parentheses and brackets are calculated at the CCSD(T)/CBS//CCSD/6-311++g(3df,2p) and CCSD(T)/CBS//CCSD(T)/6-311++g(d,p) levels of theory, respectively.

62


P2.36

Molecular Simulation of Covalent Organic Framework Formation

VU H. NGUYEN , MICHAEL GRÜNWALD

*Department of Chemistry, The University of UtahEmail: [email protected]

Covalent organic frameworks (COFs) are highly porous, crystalline materials with applications in gas storage, catalysis, and filtration. They consist of molecular building blocks held together by an intriguing balance of strong covalent bonds and weaker stacking interactions. Despite much experimental effort, assembling COFs into crystals that are ordered on length scales larger than tens of nanometers has remained a challenge. Here, we report on our efforts to elucidate the thermodynamic and kinetic bottlenecks of COF-5 formation using coarse-grained modeling and computer simulation. Our model captures important details of bond geometry and flexibility, but retains the computationally efficacy necessary to access the large time and length scales of COF nucleation and growth. Preliminary molecular dynamics results show a strong competition between covalent bond formation and stacking interactions, consistent with experimental finding.

63


P2.37

Ethane Activation on IrO2(110) surface: DFT and vdW-corrected DFT study

THONG LE MINH PHAM, 1 DUY QUANG DAO,1 DAI-VIET NGUYEN VO,2 PHAM CAM NAM,3 JYH-CHIANG JIANG4

1Institute of Research and Development, Duy Tan University, 03 Quang Trung, Danang, Viet Nam2Centre of Excellence for Advanced Research in Fluid Flow, Universiti Malaysia Pahang, 26300 Gambang,

Kuantan, Pahang, Malaysia3Department of Chemistry, Danang University of Science and Technology - The University of Danang, 54

Nguyen Luong Bang, Lien Chieu, Danang, Viet Nam4Department of Chemical Engineering, National Taiwan University of Science and Technology, 43, Keelung

Road, Section 4, Taipei 106, TaiwanEmail: [email protected] (TLMP); [email protected] (JCJ)

Ethane, the second most abundant hydrocarbon in natural gas, has recently gained enormous attention as cheap and reliable chemical feedstock owing to recent boom in shale gas and natural gas production. [1] The low-cost supply of ethane derived from above-mentioned sources makes its chemical transformation into more valuable products is of great economic attractiveness. Although ethane is chiefly used as raw material for ethylene production by steam cracking in chemical industry,[2] the full extent of ethane utilization could also be functionalization of ethane and selective conversion of ethane to ethylene, ethylene oxide, acid acetic, acetaldehyde, acrolein, vinyl chloride, ethanol etc.[3-7] Moreover, Ethane adsorption and activation is the key step in any heterogeneous catalytic processes involving in ethane chemical utilization. Therefore, it is absolutely necessary to gain insight into molecular mechanism of ethane activation on heterogeneous catalytic surfaces. In this work, theoretical calculations were performed to investigate ethane adsorption and activation on IrO2(110) surface employing both conventional and vdW-corrected density functional theory (DFT). Ethane chemical bonding to IrO2(110) surface is driven by agostic interaction of C-H bonds with Ir cus, which is involved in electron transfer from C–H bonding orbital to the empty d orbital of Ircus atom as well as back donation from the

orbital to the anti-bonding orbital of the C–H bond. The adsorption energy of ethane on IrO2(110) surface calculated by PBE funtional is 0.5eV. Vdw-corrected DFT calculation results indicate that London dispersion force enhances the adsorption energy of ethane on IrO2(110) surface by about 0.47-0.61 eV. Ethane dissociation on IrO2(110) surface is thermodynamically and kinetically favorable reaction, whose reaction energy and kinetic barrier calculated by PBE funtional are -1.13eV (-1.12eV by opt-B88 functional) and 0.50 eV (0.57eV by opt-B88 functional), respectively. By enhancing ethane adsorption energy, London dispersion force facilitates the precursor-mediated dissociation of ethane on IrO2(110) surface, which is expected to occur at relatively low temperature.

64



Figure 1. Electron density difference indicating agostic interaction between C2H6 molecule and IrO2 (110) surface and Potential energy diagram for C2H6 dissociation reaction on IrO2 (110) surface

Table 1. Adsorption energies and structural parameters of the most stable C2H6 adsorption configuration on IrO2

(110) calculated by PBE and vdW-corrected DFT functionalsDFT functionals Eads (eV) d(Ir…C) (Å) r(C-C) (Å) r(C-H) (Å)

PBE 0.50 2.70, 2.71 1.53 1.15, 1.15, 1.10vdW-DF 0.67 2.84, 2.83 1.55 1.13, 1.13 , 1.10vdW-DF2 0.72 2.95, 2.94 1.55 1.13, 1.13, 1.10

optPBE-vdW 0.97 2.71, 2.70 1.54 1.15, 1.15, 1.10optB88-vdW 1.12 2.71, 2.70 1.54 1.15, 1.15, 1.10

optB86b-vdW 1.21 2.68, 2.67 1.54 1.15, 1.15, 1.10

Keywords: Ethane adsorption, C-H activation, precursor-mediated mechanism, IrO2(110), vdW-corrected DFT

References[1] J.J. Siirola, The impact of shale gas in the chemical industry, AIChE Journal, 60 (2014) 810-819.[2] Y. Yao, D. Graziano, M. Riddle, J. Cresko, E. Masanet, Greener pathways for energy-intensive commodity

chemicals: opportunities and challenges, Current Opinion in Chemical Engineering, 6 (2014) 90-98.[3] G. Centi, F. Cavani, F. Trifirò, Selective Oxidation by Heterogeneous Catalysis, Springer US, 2001.[4] J. Gao, D. Zhou, Y. Wu, T. Wu, Direct conversion of ethane to ethylene oxide over NiAgYO catalyst,

Catalysis Communications, 30 (2013) 51-55.[5] D.J. Xiao, E.D. Bloch, J.A. Mason, W.L. Queen, M.R. Hudson, N. Planas, J. Borycz, A.L. Dzubak, P.

Verma, K. Lee, F. Bonino, V. Crocellà, J. Yano, S. Bordiga, D.G. Truhlar, L. Gagliardi, C.M. Brown, J.R. Long, Oxidation of ethane to ethanol by N2O in a metal–organic framework with coordinatively unsaturated iron(II) sites, Nat Chem, 6 (2014) 590-595.

[6] P. Verma, K.D. Vogiatzis, N. Planas, J. Borycz, D.J. Xiao, J.R. Long, L. Gagliardi, D.G. Truhlar, Mechanism of Oxidation of Ethane to Ethanol at Iron(IV)–Oxo Sites in Magnesium-Diluted Fe2(dobdc), Journal of the American Chemical Society, 137 (2015) 5770-5781.

[7] Z. Zhao, Y. Yamada, Y. Teng, A. Ueda, K. Nakagawa, T. Kobayashi, Selective Oxidation of Ethane to Acetaldehyde and Acrolein over Silica-Supported Vanadium Catalysts Using Oxygen as Oxidant, Journal of Catalysis, 190 (2000) 215-227.

65


P2.38

Formation of Two-Dimensional Amorphous Silicon Carbide from the Melt

LE NGUYEN TUE MINH , VO VAN HOANG

Computational Physics Lab, HCM City Univ. of Technology268 Ly Thuong Kiet Street, District 10, HochiMinh City-Vietnam


The glass formation of two-dimensional Silicon Carbide with the Tersoff interatomic potential is studied by molecular dynamics (MD) simulation. Supercooled and glassy states are obtained by cooling from the melt. Structural properties are investigated via partial radial distribution function (PRDF), coordination number and ring distributions. Structural defects and their role in structure and properties of two-dimensional SiC have been analyzed and discussed. We also show temperature dependence of various thermodynamic quantities of the system. Calculations show that although amorphous two-dimensional SiC also exhibits honeycomb-like structure (sixfold rings are main structural blocks), Si and C atoms are randomly distributed in the rings unlike that found for crystalline counterpart. In addition, amorphous two-dimensional SiC contains a large amount of structural defects which may lead to quite different physico-chemical behaviors compared to those of crystalline one.

Keywords: Glass Formation, Two-Dimensional Silicon Carbide, Structural Defects

66



P2.39

A Synergistic Effect of Hydrogenation and SCN Treatments of Ag-loaded TiO2 NPs on Water Splitting

T. T WANG, P. RAGHUNATH, M. C. LIN*

Center for Interdisciplinary Molecular Science, Department of Applied Chemistry,National Chiao Tung University, Hsinchu 300, Taiwan

Emails: [email protected] (PR); [email protected] (MCL)

Although silver is less reactive as a catalyst for water splitting than Pt and Au, Choi et al. [ACS Catal. 2016, 6, 821] have revealed that the SCN-treatment of Ag-loaded on TiO2 nanoparticles enhances its hydrogen production efficiency by 4 times. In this work, we have discovered that the hydrogenation of TiO2 NPs further enhances the efficiency of AgSCN/TiO2 by a factor of 3 with an overall solar to hydrogen efficiency of 7.0% using a Pyrex tube with a <3.25 W Xe-lamp from a 500W Xe-lamp.Experimentally, the hydrogenated TiO2 (H:TiO2) NPs were first prepared with 3 hours of hydrogenation at 300 ºC with 150 Torr methanol vapor as H source. Silver ion from AgNO3 was reduced on H:TiO2 NPs in methanol solution with 30 min Xe-lamp irradiation. For water splitting reaction, 30 mg substrate was dissolved in a reactor with 60ml DIW and 20% methanol as sacrificial reagent. For Ag/H:TiO2 NPs, H2 production rate was found to increase by 15 times over that of H:TiO2 (see Fig. 1). SCN treatment of Ag/H:TiO2 further enhanced the efficiency by 3 times. H2 production rate remained unchanged after 6 consecutive weeks of durability test (carried out once per week), including a full week solar irradiation, revealing the durability of the AgSCN/H:TiO2 system. Computationally, we have investigated the adsorption of SCN and the reaction of H on Ag-loaded anatase TiO2(101) surface using spin-polarized density functional theory (DFT) employing the PBE functional. The SCN adsorption energy for on the Ag/TiO2 was found to be 43.0 kcal/mol for 1 SCN on 1Ag and 60.2 kcal/mol for 2 SCN on 3Ag atoms. H atom can directly form an N−H bond with large exothermicity (-67.9 kca/mol) when compared to an S−H bond (-46.9 kca/mol). The results show that, an additional H atom can directly abstract the H atom of TiO2-1Ag-SCNH or TiO2-1Ag-S(H)CN to release H2 through 10.2 or 4.6 kcal/mol barriers, respectively. In the case of 2 SCN on 3 Ag loaded TiO2, H2 elimination from 2 N−H and 2 S−H sides required 52.8 kcal/mol and 6.9 kcal/mol, respectively. The predicted densities of states show several prominent new impurity states in the band gap of AgSCN/H:TiO2.

Figure 1. a) Hydrogen production rate comparison for TiO2, H:TiO2, Ag/TiO2, AgSCN/TiO2, Ag/H:TiO2, AgSCN/H:TiO2 as labelled. b) Schematic diagram of H atom binding on SCN and H2 elimination by DFT method.

67

0 20 40 60 80 100

0

10

20

30

40

50

60

70

80

[H2]

/m

ol

Time /min

TiO2 HTiO2 AgTiO2 AgSCNTiO2 AgHTiO2 AgSCNHTiO2

a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)a)



P2.40

Theoretical Study of the Influence of Saturated Hydrocarbons Over Dye Adsorption in Dyes-Sensitized Solar Cells Application

THI M. T. NGUYEN, 1 HA H. DO,1 NGUYEN-NGUYEN PHAM-TRAN1,2

1 Institute for Computational Science And Technology at Ho Chi Minh City, Quang Trung Software City, SBI Building. Street No. 3, Tan Chanh Hiep Ward, District 12, HCMC.

2 Laboratory of Computational Chemistry, Faculty of Chemistry, University of Science, Vietnam National University – Ho Chi Minh City,227 Nguyen Van Cu, District 5, HCMC.


Three organic dyes, named 2-4, were designed followed D-π-A model, the most common dye formation has been used in dye-sensitized solar cells (DSSCs). Without heterocycles in the conjugations, theoretical dye molar extinction coefficients in DMF were merely different, 340.3 (2) and 340.4 nm (3 and 4) with PCM model at TD-DFT/MPW1K/6-31G* level. Furthermore, the study carried out the influence of alkyl chains on dye adsorption onto TiO2 semiconductor surface with (1 0 1) direction. With the prolongation of alkyl chains in charge pushing groups, from four to eight saturated carbons, these dyes adsorbed at the interfaces without regulation. To investigate the dependence of adsorption positions, each dye adsorption was modeled in two forms. Adsorption energies were ~ 0.9 kcal/mol (2), ~ 18.5 kcal/mol (3) and ~ -15.8 kcal/mol (4). The energy deviations between two adsorbed positions were not significant (~ 0.001- 0.01 kcal/mol). Based on the computational results, with the purpose of experimental backup, we suggested that prolonging alkyl chains mainly prevented dye aggregation and the use of longer alkyl chains to improve the power conversion efficiencies (PCEs) were not regular. Moreover, the adsorbed positions were negligibly dependent on sizes of alkyl chains and it was considered as the minor influence to dye adsorption.

Keywords: DSSCs, PCEs, DSC, PCM, TD-DFT, D-π-A

68


P2.412

Density Functional Studies on Mechanisms of Alkaline Hydrolysis Reactions of Lactam Antibiotics Models

NGUYEN HOA MI ,1 NGUYEN THI NGOC HONG,1 SEIJI MORI2 1VNU University of Science, Ha Noi, Vietnam

2 Ibaraki University, JapanEmail: [email protected]

β-Lactam resistance of methicillin-resistant Staphylococcus aureus (MRSA), a pathogenic bacterium that causes staph infections, represents a serious threat to public health. Previous researches indicated that the mechanism of β-lactam resistance was related to the process of cleaving the C-N bond of β-lactam ring. Numerous researches were devoted to the hydrolytic ring-opening reaction mechanism of β-lactam, which proved that the mechanism of enzymatic hydrolysis is similar to that of alkaline hydrolysis.Mechanism of the alkaline hydrolysis reactions of lactam models were proposed to take place in two basic steps: The first step of the reaction mechanism involves the nucleophilicity of the hydroxyl ion group to promote the C-O bond formation. The second step involves the simultaneous breaking of C–N bond and a proton transfer from a hydroxyl group to nitrogen atom to yield the product (Figure 1).

Figure 1. Acylation mechanism in which the lactam carbonyl is attacked by (OH-) in solution.

All calculations were carried out with the Gaussian 09 package. Geometry optimizations in soluiton were carried out the B3LYP-D3 method with 6-311+G** basis set. The alkaline hydrolysis reaction was performed in aqueous phase using the self-consistent reaction field (SCRF) method based on SMD theory with water solvent (ε=78.3553).

69


P2.42

QSPR Studies of Organic Dyes Using First-Principles and Artificial Neuron Network:

Predicting Tools for Energy Conversion Efficiency of Dyes-Sensitized Solar Cells

Phuc T. N. Tu, 1, Thanh N. Tran,1 Loan T. T. Nguyen,1 Van K. T. Nguyen,1

Thi M. T. Nguyen,2 Nguyen-Nguyen Pham-Tran1,2

1Laboratory of Computational Chemistry, Faculty of Chemistry, University of Science, Vietnam National University – Ho Chi Minh City,227 Nguyen Van Cu, District 5, HCMC.

2Institute for Computational Science And Technology at Ho Chi Minh City, Quang Trung Software City, SBI Building. Street No. 3, Tan Chanh Hiep Ward, District 12, HCMC.


AbstractIn this work, we take the advantage of computational chemistry, as well as chemoinformatic in solving practical problems of developing high potential organic dyes for dye-sensitized solar cells (DSSC) application. The outcome of our project is to build a good QSPR (Quantitative Structure Property Relationships) model of series organic dyes which has accurately predicting energy conversion efficiency of DSC based on parameter-free from first principles calculations. This will be a powerful support tool for virtual screening and testing new dyes for DSC and suggesting the promising candidates for actual experimental synthesis.

Keywords: Chemoinformatic, QSPR, DSC, ANN, GA, First principles calculations

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