xxxvi reunión bienal real sociedad española de física santiago...
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XXXVI Reunión Bienal Real Sociedad Española de FísicaSantiago de Compostela, 17-21 de julio de 2017
Symposium (GEFAM) “MOLECULAR PHYSICS IN THE EDGE”
PROGRAM
TALKS, Tuesday, 18th.
Chairpersons: M. I. Hernández and J. Campos Martínez
15:1015:15 Welcome (J. Campos Martínez, M. Bartolomei, M. I. Hernández)
15:1515:45 (Invited)
HALBERSTADT, Nadine (U. Toulouse): Theoretical study of the dynamics of superfluid helium nanodroplets doped with alkali atoms
15:4516:05 COLETTI, Cecilia (U. ChietiPescara): Structure and dynamics of ions in gas phase: interplay between experiments and theory in IRMPD spectroscopy
16:0516:25 MARTÍNEZ HAYA, Bruno (U. Pablo Olavide): The quest towards supramolecular networks from first principles
16:2516:45 LOMBARDI, Andrea (U. Perugia): Energy transfer in gaseous mixtures for atmospheric and astrochemical modelling
16:4517:05 MARTÍNEZNUÑEZ, Emilio (U. S. Compostela): Automated discovery of reaction mechanisms and kinetics using dynamics simulations
17:0517:30 Coffee Break
17:3018:00(Invited)
VON HAEFTEN, Klaus (Leicester): Exploring molecular interactions in the condensed phase with full rotational resolution
18:0018:20 MARTÍN PENDÁS, Ángel (U. Oviedo): Intrinsic Bond Energies: A real space point of view
18:2018:40 SARSA, Antonio (U. Córdoba): Continuous spectrum of the H atom after confinement
18:4019:00 HUARTELARRAÑAGA, Fermin (U. Barcelona): Hydrogen diffusion along SWCNTs: Timescale separation and tunneling Effects
19:0019:20 DE LARA CASTELLS, Maria Pilar (IFFCSIC): Quantum nuclear motion of Helium and molecular nitrogen clusters in carbon nanotubes
TALKS, Wednesday, 19th.
Chairpersons: M. Bartolomei and J. Bretón.
15:1515:45(Invited)
PIRANI, Fernando (U. Perugia): Experimental characterization of the basic intermolecular interaction components
15:4516:05 VAN HULST, Niek F. (ICFO): Ultrafast broadband transient absorption spectroscopy of a single molecule
16:0516:25 FERNÁNDEZ, José M. (IEMCSIC): Laboratory study of inelastic collisionsof O2 with He at low temperature
16:2516:45 PÉREZ DE TUDELA, Ricardo (U. Bochum): Acid dissociation in microsolvated environments
16:4517:05 GIORGI, Giacomo (U. Perugia): Hybrid organicinorganic halide perovskites for photovoltaics and lasing applications: Insights from first principles calculations
17:0517:30 Coffee Break
17:3018:00(Invited)
MARQUES, Jorge (U. Coimbra): Revealing the lowenergy landscape of clusters: from the solvation of ions to the selfassembling of colloidal particles
18:0018:20 HERNÁNDEZROJAS, Javier (U. La Laguna): Coarsegraining polycyclic aromatic hydrocarbon clusters
18:2018:40 GONZÁLEZ, Eva (IQFRCSIC): Experimental and simulation studies of the stepped adsorption of gases on silicalite2
18:4019:00 OTERO MATO, José Manuel (U. S. Compostela): Computational study ofmixtures of ILs and alcohols under nanoconfinement conditions
POSTERS
ARTEAGA GUTIÉRREZ, Kilian (IFFCSIC): Rare gas adsorption on naphthalene: Ab initio intermolecular potentials and cluster configurations
BARTOLOMEI, Massimiliano (IFFCSIC): Novel nanoporous graphites for gas storage and release
CAMPOSMARTÍNEZ, José (IFFCSIC): Quantummechanical simulations of the transport of atoms through nanoporous membranes
CUEVASFLORES, Ma del Refugio (IFFCSIC): Noncovalent interactions between cisplatin and graphene prototypes
DOCAMPO ÁLVAREZ, Borja (U. S. Compostela): Molecular dynamics study of mixtures of protic and aprotic ILs and the effects of alkyl chain length
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nº
Molecular Physics at the Edge
Theoretical study of the dynamics of superfluid helium nanodroplets
doped with alkali atoms M. Martinez1, F. Coppens1, M. Barranco1,2,3, N. Halberstadt1,*, and M. Pi2,3
1 LCAR-IRSAMC, Université Toulouse III Paul Sabatier, CNRS, 118 route de Narbonne, F-31062 Toulouse Cedex 09, France 2 Departament FQA, Facultat de Física, Universitat de Barcelona. Diagonal 645, 08028 Barcelona, Spain 3 Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona
* [email protected] Helium nanodroplets are large helium clusters (typically thousand to several hundered
thousand atoms) exhibiting remarkable properties : very low temperature (0.4 K), superfluidity, weak interaction with the dopant, very high thermal conductivity and very fast relaxation dynamics. This makes them an exceptional environment for dynamics studies [1].
During the past few years, several real time dynamics experiments have been conducted on
these systems thanks to femtosecond pump-probe laser techniques [2]. Alkali atoms are particularly interesting as dopants because of their very weakly attractive interaction with helium, which makes them reside in a dimple at the droplet surface [3,4]. Upon photoexcitation they usually desorb [3], except the heavy alkalis Rb and Cs excited close to the gas phase D1 transition [5, 6]. This is due to the strong repulsion between the electronic orbital (much more diffuse in the excited state) and the surrounding helium. The process can be rather complex, since the nanodroplet can absorb and dissipate part of the recoil energy as density waves, atom fast dissociation or evaporation, or even vortex ring nucleation. In addition, the alkali atom can bring along one or a few helium atoms and desorb as an exciplex [2,7].
From a theoretical point of view, the light mass of helium makes it a challenge to study the real time dynamics of this process because of quantum effects. The Helium density functional theory (He-DFT) approach and its time-dependent version (He-TDDFT) are very efficient semi-empirical methods which work with the helium density rather than the N-helium wave function, like quantum chemistry DFT does with electron density. They have proven to be the only way to date to simulate both the stability and the dynamics of a droplet with a size comparable to experiment [8, 9].
We present a theoretical study of alkali excitation : K to (4p) and (5s), Rb (5p) and (6p), on
helium droplets. Calculations are based on the combination of classical dynamics for the dopant and quantum time-dependent density functional theory (TDDFT) for helium. In the case of Rb [10], the simulations are confronted with femtosecond imaging spectroscopy experiments. We disentangle the competing dynamics of excited Rb desorption and solvation inside the droplet as it gets ionized. In the case of K (5s) excitation, the effect of treating the potassium atom quantum mechanically is explored [11].
Acknowledgments
Financial support for this work Spain (grant no. FIS2014-52285-C2-1-P), and HPC resources from CALMIP (Grant P1039) is gratefully acknowledged. M.B. thanks the Université Fédérale Toulouse Midi-Pyrénées for financial support through the “ Chaires d’ Attractivité 2014” program IMDYNHE.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nº
Molecular Physics at the Edge
References [1] S. Grebenev, J.P. Toennies, A.F. Vilesov, Science 279 (1998) 2083. [2] M. Mudrich, F. Stienkemeier Int. Rev. Phys. Chem. 33 (2014) 301. [3] F. Ancilotto, E. Cheng, M.W. Cole, F. Toigo, Z. Phys. B 98 (1995) 323. [4] F. Stienkemeier, J. Higgins, C. Callegari, S. I. Kanorsky, W. E. Ernst, G. Scoles, Z. Phys. D 38 (1996) 253. [5] G. Auböck, J. Nagl, C. Callegari, W. E. Ernst, Phys. Rev. Lett. 101 (2008) 035301. [6] M. Theisen, F. Lackner, W. E. Ernst, J. Chem. Phys. 135 (2011) 074306. [7] F. Stienkemeier, K. K. Lehmann, J. Phys. B: At. Mol. Opt. Phys. 39 (2006) 127. [8] M. Barranco, R. Guardiola, E. S. Hernández, R. Mayol, J. Navarro and M. Pi, J. Low Temp. Phys. 142 (2006) 1. [9] F. Ancilotto, M. Barranco, F. Coppens, J. Eloranta, N. Halberstadt, A. Hernando, D. Mateo, M. Pi, to be published [10] J. von Vangerow, F. Coppens, A. Leal, M. Pi, M. Barranco, N. Halberstadt, F. Stienkemeier, M. Mudrich, J. Phys. Chem. Lett. 8 (2017) 307. [11] M. Martinez, F. Coppens, N. Halberestadt, M. Barranco, M. Pi, to be published.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºSimposium Title
Structure and dynamics of ions in gas phase: interplay between experiments and
theory in IRMPD spectroscopy
R. Paciotti1, D. Corinti2, M.E. Crestoni2, S. Fornarini2, N.Re1, C.Coletti1*
1 Dipartimento di Farmacia, Università G. d’Annunzio Chieti-Pescara, Via dei Vestini, I-66100 Chieti, Italy2 2Dipartimento di Chimica e Tecnologie del Farmaco, Università di Roma La Sapienza, P.le A. Moro 5 - Roma
IR vibrational spectroscopy is a widespread technique for the characterization of molecules ingas phase, highly sensitive to small structural changes, like hydrogen bonding patterns, thusallowing the detection of motifs and signatures occurring in relevant processes. In the case ofgaseous ions, the low density of the sampled species requires the use of a sensitive 'action'spectroscopy approach such as IRMPD (IR Multiple Photon Dissociation) spectroscopy. By thistechnique the fragmentation due to absorption of multiple IR photons in resonance with activevibrational modes of the molecular ion is probed by mass spectrometry. The IRMPD spectrum isthen obtained by reporting photo-fragmentation yield as a function of the IR photon energy.
The interpretation of the experimental spectra needs in any case a strong computational supportto correctly assign the main features to the corresponding vibrational modes and to identify thepopulated isomers and/or conformers, particularly when flexible molecule are investigated [1,2].This combined approach has recently allowed a comprehensive description at the molecular levelfor the reactive events responsible for cisplatin activity [3,4], including the first direct evidence of aprototypical Eigen-Wilkins encounter complex in solution [5].
The last years have also witnessed increasing applications of IRMPD kinetics experiments,where the use of selected active IR photons can produce selective photo-fragmentation of differentisomers or even different conformers [6], thus enabling the qualitative and quantitativecharacterization of their population in the experimental mixture.
References
[1] C. Coletti, N. Re, D. Scuderi, P. Maitre, B. Chiavarino, S. Fornarini, F. Lanucara, R.K. Sinha, M.E. Crestoni, PhysChemChemPhys 12 (2010) 13455.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºSimposium Title
[2] R. Paciotti, C. Coletti, N. Re, D. Scuderi, B. Chiavarino, S. Fornarini, M.E. Crestoni, PhysChemChemPhys 17 (2015) 25891.[3] A. De Petris, A. Ciavardini, C. Coletti, N. Re, B. Chiavarino, M.E. Crestoni, S. Fornarini, J Phys. Chem. Lett. 4 (2013) 3631.[4] D. Corinti, C. Coletti, N. Re, S. Piccirillo, M. Giampà, M.E. Crestoni, S. Fornarini, RSC Adv. 7 (2017) 15877. [5] D. Corinti, C. Coletti, N. Re, B. Chiavarino, M.E. Crestoni, S. Fornarini S, Chem.: Eur. J. 22 (2016) 3794.[6] D. Corinti, A. De Petris, C. Coletti, N. Re, B. Chiavarino, M.E. Crestoni, S. Fornarini, ChemPhysChem 18 (2017) 318.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nº 1 Simposium: Molecular Physics at the Edge
The quest towards supramolecular networks from first principles
B. Martínez-Haya*, Juan R. Avilés-Moreno
Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, E41013 Seville, Spain
* corresponding autor: [email protected]
How far into molecular complexity can we get from first principles? Can we predict specific
recognitions between molecules from the computation of the relevant conformations and interactions? Is it then possible to forsee how assemblies of molecules spontaneously conform functional nanostructures and materials? Will we ever understand the behaviour of living organisms from the investigation of their molecular building blocks? Should we even dare? These are challenging but central questions in the scientific activity of chemical physicist. [1,2]
Figure 1: The path towards chemical complexity through the investigation of isolated supramolecular systems.
A modest illustration of this topic can be obtained from an overview of the incursions of our
group into molecular recognition and supramolecular aggregation over the last decade. Our approach has been invariably based on the characterization of isolated supramolecular complexes with laser action vibrational spectroscopy and mass spectrometry experimental techniques, in combination with quantum chemical computations based on density functional theory and on ab initio perturbative MP2 methods. The spectroscopy experiments are performed on cationic or anionic complexes that are typically mass-selected and stored in an ion trap under well defined environmental conditions. A main advantage of this approach is that the chemical system under study is well defined and can be incorporated without ambiguity into the quantum chemical models. In this way, insights into the intrinsic interactions and conformational constraints that sustain the formation of the complexes can be obtained, and the accuracy of the computational methods can be evaluated, leading to preliminary assessments about their potential performance in solution and further condensed phases.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nº 2 Simposium: Molecular Physics at the Edge
Our research has primarily focused on inclusion complexes, in which a charged guest species inserts into a molecular cavity. We have investigated an ample ensemble of host macrocycle cavities, such as crown ethers, nactins, cyclodextrins, valynomicin or calixarenes. Moreover, guest species of varying complexity have been considered, namely alkali, alkaline-earth and transition metal cations, halide and phosphate anions, and protonated amines and aminoacids. A schematic representation of the variety of complexes investigated is depicted in Fig.1. Apart from their interest in the chemical and pharmaceutical industries, these supramolecular systems constitute excellent benchmarks for experimentation and quantum chemical modelling.
In order to illustrate the potential of this type of investigations with isolated complexes, a brief reference is made below to a number of fundamental (bio)chemical issues for which the combination of spectroscopy and computations in our group has provided (we hope) relevant microscopic information:
• Microsolvation [3,4]: What are the preferential hydration domains of a complex molecule? How many water molecules make a solution? How does the binding selectivity and molecular conformations change from gas-phase to solution? What behavior can be expected in intermediate cases, e.g. for semi-solvated complexes at the solution-air interface?
• Cation/anion ditopic binding [5]: What are the optimum structural features of a molecular cavity for the simultaneous binding of ion pairs? What correlation is required beween the conformations adopted by the host macrocycle in the individual cationic and anionic complexes?
• Localization of charge, proton bridges and proton transfer [6]: What are the structural and spectral features of proton sharing in non-covalent complexes? How does host-guest proton transfer affect supramolecular recognition?
• Molecular tweezers [7]: What can be learned from isolated complexes about the taylored design of molecular tools, such as tweezers to “grab” specific chemical species from a solution?
• Chirality [8,9]: What are the conformational constraints that drive enantiomeric recognition? How can chirality emerge in the complexation of non-chiral host and guest species?
A number of brilliant team members and external collaborators have contributed to this research over the last decade. We are particularly thankful to Ana R. Hortal, P. Hurtado and F. Gámez at Universidad Pablo de Olavide, as well as to J. Oomens (Univ. Nijmegen), K. Dreisewerd (Univ. Munster), S. Schlemmer (Univ. Cologne), J.J. López-González (Univ. Jaén), L. Bañares and F.J. Aoiz (Univ. Complutense). Funding has been provided over the years by different research programmes of the Government of Spain, Junta de Andalucía and FEDER.
References
[1] J.-P. Schermann, Spectroscopy and Modelling of Biomolecular Building Blocks, Elsevier B.V., Amsterdam 2008. [2] B. Martínez-Haya, An. Quím. 107, (2011), 367. [3] B. Martínez-Haya, J.R. Avilés-Moreno, S. Hamad, J. Elguero, Phys. Chem. Chem. Phys.,19, (2017), 1288. [4] F. Rodrigo, F. Gámez, J.R. Avilés-Moreno, J.M. Pedrosa, B. Martínez-Haya, Phys. Chem. Chem. Phys., 18, (2016), 3497. [5] J.R. Avilés-Moreno, G. Berden, J. Oomens, B. Martínez-Haya, ChemPhysChem, 18, (2017), in press. [6] P. Hurtado, F. Gámez, S. Hamad, B. Martínez-Haya, J.D. Steill, J. Oomens, J. Phys. Chem. A, 115 (2011) 7275. [7] F. Gámez, P. Hurtado, S. Hamad, B. Martínez-Haya, G. Berden, J. Oomens, B. Martínez-Haya, ChemPhysChem, 77, (2012), 118. [8] J.R. Aviles-Moreno, M.M. Quesada-Moreno, J.J. Lopez-Gonzalez, B. Martínez-Haya, J. Phys. Chem. B 117, (2013), 9362. [9] B. Martínez-Haya, P. Hurtado, A.R. Hortal, S. Hamad, J.D. Steill, J. Oomens, J Phys Chem A. 114, (2010), 7048.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºMolecular Physics at the Edge
Energy transfer in gaseous mixtures for atmospheric and astrochemical
modelling
A. Lombardi1,*, M. Bartolomei2, F. Pirani1
1 Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto 8, 06123, Perugia, Italy2 Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 123, Madrid, Spain
The development of realistic kinetic models of gaseous systems is a fundamental issue in the study of Earth and planetary atmospheres, plasma chemistry, gas flows and astrochemistry. Particularly, the adoption of a state-to-state level of detail in the description of the molecular energy transfer [1,2], a desirable and necessary improvement, requires much insight into the dynamics of the inelastic collisions and the prompt availability of state-specific energy transfer probabilities and ratecoefficients. Existing venerable approximated theories of the energy transfer, such as the Schwartz-Slawsky-Herzfeld one, are not really state-specific and have limited validity. Therefore probabilitiesand cross sections have to be calculated directly by simulation of the dynamics of the molecular collisions. The reliability of the simulations is conditional to the availability of accurate descriptionsof the intermolecular interactions occurring between pairs of the molecular species present in the gas mixture. Here, we present examples of calculation of rate coefficients of energy transfer in mixtures containing CO2 and N2 [3-6] obtained applying a semiempirical approach to the interactionmodelling, based on (i) a physically meaningful partition of the contribution to the interaction, (ii) the use of data from molecular beam experiments and (iii) ab initio calculations. An extension of such an approach can be also applied to the modelling dynamics and kinetics of gas-surface systems.
Acknowledgments
A. L. acknowledges financial support from the Dipartimento di Chimica, Biologia eBiotecnologie dellUniversita di Perugia (FRB, Fondo per la Ricerca di Base), from MIUR PRIN2010/2011 (contract 2010ERFKXL 002) and from “Fondazione Cassa Risparmio Perugia (CodiceProgetto: 2015.0331.021 Ricerca Scientifica e Tecnologica)”. A. L. and F. P. acknowledge theItalian Ministry for Education, University and Research, MIUR, for financial supporting: SIR 2014“Scientific Independence for young Researchers” (RBSI14U3VF) and financial support from MIURPRIN 2015 (contract 2015F59J3R 002).
References
[1] Capitelli, M., Ferreira, C. M., Gordiets, B. F., Osipov, R.: Plasma kinetics in atmospheric gases; Springer Verlag,2000. [2] E. Kustova, E. Nagnibeda, State-to-state theory of vibrational kinetics and dissociation in three-atomic gases; InRarefied Gas Dynamics; T. Bartel, M. Gallis, Eds.; AIP Conference Proceedings, Vol. 585, pp. 620–627, IOPPublishing, Bristol, England, 2001. [3] M. Bartolomei, F. Pirani, A. Lagana, A. Lombardi, A full dimensional grid empowered simulation of the CO2 + CO2processes, J. Comput. Chem. 33 (2012) 1806. [4] A. Lombardi, N. Faginas Lago, A. Laganà, F. Pirani, S. Falcinelli, Lecture Notes in Computer Science 7333 Part I(2012) 387.[5] A. Lombardi, N. Faginas-Lago, L. Pacifici, A. Costantini, Modeling of energy transfer from vibrationally excitedCO2 molecules: cross sections and probabilities for kinetic modeling of atmospheres, flows, and plasmas, J. Phys.Chem. A 117 (2013) 11430.[6] A. Lombardi, F. Pirani, A. Laganà, M. Bartolomei Energy Transfer Dynamics and Kinetics of Elementary Processes(Promoted) by Gas-Phase CO2-N2 Collisions: Selectivity Control by the Anisotropy of the Interaction 33 J. Comp.Chem. (2016) 1463.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºMolecular Physics at the Edge
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºSimposium Title
Automated Discovery of Reaction Mechanisms and Kinetics Using Dynamics
Simulations
E. Martínez-Núñez
Departmento de Química Física, Facultade de Química, Universidade de Santiago de Compostela, 15782, Santiago de Compostela
A novel computational method is proposed in this talk for use in discovering reactionmechanisms and solving the kinetics in reactive systems [1,2]. The method does not rely on eitherchemical intuition or assumed a priori mechanisms, and it works in a fully automated fashion. It hastwo components: accelerated chemical dynamics simulations and a post-processing geometry-basedalgorithm that selects suitable transition state (TS) guess structures.
Two levels of electronic structure calculations are involved in the procedure: a low level (LL)is used to integrate the trajectories and to optimize the TSs, and a higher level (HL) is used to refinethe structures.
Our method has been successfully employed in the study the dissociation channels offormaldehyde, formic acid (FA), vinyl cyanide (VC), propenal, acryloyl chloride (AC), andprotonated uracil (uracil-H+), and also in the study the cobalt-catalyzed hydroformylation andhydrogenation of ethylene [3].
Figure 1 shows a flow-chart outlining the different steps of the automated method needed tostudy organometallic catalysis.
Figure 1: Flow-chart outlining the different steps of the automated method presented in this talk tostudy organometallic catalysis.
References
[1] E. Martínez-Núñez, J. Comput. Chem. 36 (2015) 222.[2] E. Martínez-Núñez, Phys. Chem. Chem. Phys. 17 (2015) 14912. [3] J. A. Varela, S. A. Vázquez, and E. Martínez-Núñez, Chem. Sci., DOI: 10.1039/C7SC00549K
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nº
Simposium Title
Exploring molecular interactions in the condensed phase with full rotational
resolution
Klaus von Haeften1,*, Luis G. Mendoza Luna2, Nagham Shiltagh2, Gediminas Galinis2, Russell S. Minns3, Andrew M.
Ellis4, Mirjana Mladenović5, Marius Lewerenz5, Nelly Bonifaci6 , Frédéric Aitken7, Mark Watkins2, Emma Springate8,
Cephise Cacho8, Richard T. Chapman8, I. C. Edmond Turcu8, Arnaud Rouzée9, Jonathan G. Underwood10
1Knano, Leicester, LE2 1YA, United Kingdom
2University of Leicester, Department of Physics & Astronomy, Leicester, LE1 7RH, United Kingdom
3University of Southampton, Chemistry, Southampton, SO17 1BJ, United Kingdom
4University of Leicester, Department of Chemistry, Leicester, LE1 7RH, United Kingdom
5Université ParisEst, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR8208 CNRS, 5 bd Descartes, 77454 MarnelaVallée, France
6G2ELabGreEnER, Equipe MDE, 21 avenue des Martyrs, CS 90624, 38031 Grenoble Cedex 1, France
7Central Laser Facility, STFC Rutherford Appleton Laboratory, United Kingdom
8Max Born Institute, Max Born Strasse 2A, 12489 Berlin, Germany
9Department of Physics & Astronomy, University College London, London WC1E 6BT, United Kingdom
Introduction
The interaction of molecules determines chemical reactions and biological processes. Very finedetails of such interactions can be unravelled using rotational spectroscopy thanks to its greatresolving power. However, rotational spectroscopy is usually restricted to the gas phase. In thecondensed phases, interactions are usually so strong that rotational features are overshadowed. Anexception is liquid helium where interactions are exceptionally weak. Furthermore, its properties arestrongly affected by quantum effects. Also, it is an attractive model substance for theory and forexperiment: (i) helium atoms, having only two electrons, greatly facilitate high level ab initiocalculations of clusters. (ii) At the temperatures where helium becomes liquid all other substancesfreeze. Liquid helium is therefore one of the purest, if not the purest of all condensed substances.This exceptional purity has recently been exploited for the investigation of nucleation, growth andsolidification of nanoparticles [1].
This presentation will highlight two recent experiments where rotational spectroscopy has beenpushed to new limits. The full rotational spectrum of a molecular complex was derived usingfemtosecond wave packet spectroscopy. In another experiment in liquid helium, molecules wereidentified in their lowest rotational quantum state in thermal equilibrium.
Impulsive alignment of clusters in a beam and fluorescence spectroscopy in bulk helium
We have excited a supersonic beam of small C2H2-Hen clusters non-resonantly with intensefemtosecond laser pulses - a technique called impulsive alignment - thereby creating wave packetscomposed of rotational eigenstates. The clusters were then probed with a second laser pulse after aset time delay which led to Coulomb explosion. Using the fragment velocity distribution of theC2H2 molecules the state of alignment was determined and the propagation of rotational wavepackets was measured in the time domain. A Fourier-transform of the time-spectrum yielded the
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nº
Simposium Title
pure complete rotational spectrum of C2H2-He in excellent agreement with theory [2]. The spectrumshowed strong delocalisation of the complex indicating liquid-like character. The excited complexnevertheless rotated coherently over the entire duration of the experiment of 600 ps and showed nosigns of dephasing [3].
These results demonstrate that impulsive alignment is well suited to derive structural anddynamical information from clusters, including weakly bound complexes. Production of thesecomplexes requires strong cooling with the consequence that normally only the lowest rotationalquantum states are populated. Unlike traditional frequency domain spectroscopy, where selectionrules limit the quantum number of states to ΔJ=1, impulsive alignment provides the control that isnecessary to excite and probe all J levels, up to the dissociation threshold.
In another experiment bulk helium was electronically excited using a corona discharge,creating a rich fluorescence spectrum which was measured as a function of temperature andpressure. Intense fluorescence in the visible region showed the rotationally resolved d u
+ b3g
transition of He2*. With increasing pressure, the rotational lines merged into single features. The
observed pressure dependence of line width, shapes and line shifts established that within liquidhelium excimers are either solvated, and cold, or ‘boiling’ within rotationally hot gas pockets.Increase of hydrostatic pressure was found to rotationally cool the excimers at a rate of at least 1010
to 1011 K/s in collisions with the liquids until they occupied the lowest available quantum state [4].
These findings are important with regard to the quest of achieving greatest possible controlover molecules, including cooling their degrees of freedom. Also, they suggest that it should bepossible to investigate liquid and superfluid helium at the nanoscale over a large pressure andtemperature range using molecules as rotational probes. Previous experiments used helium dropletsand were therefore restricted to fixed pressures and temperatures. They suggest that by additionalcontrol of pressure, temperature and thermodynamic phase unprecedented insight into the structureof solvation layers and interfaces can be achieved.
Funding is acknowledged from the Royal Society, The Leverhulme Trust, Erasmus, COSTaction MOLIM, CONACYT, the Iraq government and the University Joseph Fourier for a visitingprofessorship for KvH.
References
[1] H. Gharbi Tarchouna, N. Bonifaci, F. Aitken, L. G. Mendoza-Luna, and K. von Haeften, J. Phys. Chem. Lett. 6(2015) 3036
[2] G. Galinis, L. G. Mendoza-Luna, M. J. Watkins, C. Cacho, R. T. Chapman, A. M. Ellis, M. Lewerenz, L. G.Mendoza Luna, R. S. Minns, M. Mladenovic, E. Springate, I. C. E. Turcu, M. J. Watkins, L. Kazak, S. Gode, R. Irsig, S.Skruszewicz, J. Tiggesbaumker, K-H. Meiwes-Broer, A. Rouzee, J. G. Underwood, M. Siano and K. von Haeften,Faraday Discuss. 171 (2014) 195
[3] G. Galinis, L. G. Mendoza-Luna, M. J. Watkins, C. Cacho, R. T. Chapman, A. M. Ellis, M. Lewerenz, L. G.Mendoza Luna, R. S. Minns, M. Mladenovic, A. Rouzee, E. Springate, I. C. E. Turcu, M. J. Watkins, and K. vonHaeften, Phys Rev. Lett. 113 (2014) 043004
[4] L. G. Mendoza-Luna, N. M. K. Shiltagh, M. J. Watkins, N. Bonifaci, F. Aitken, and K. von Haeften, J. Phys. Chem.Lett. 7 (2016) 4666
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºSimposium Title
Intrinsic Bond Energies: A real space point of view
A. Martín Pendás1,*, D. Menéndez Crespo1, E. Francisco1
1 Departamento de Química Física y Analítica. Universidad de Oviedo
A not completely extinguished fire on the nature of the chemical bond in the C2 molecule [1]has re-openened several dormant fronts on the interpretation of bond energies. One of these regardswhether we should measure bond strengths with respect to the ground states of the isolatedfragments that become bonded, leading to standard bond dissociation energies (BDE), or ifappropriately "prepared for bonding", i.e. excited, states should be used instead. The latter viewprovides larger bond energies, which are usually called intrinsic bond energies (IBE) [2]. Here weexamine this problem from a real space partitioning point of view, using the Interacting QuantumAtoms (IQA) approach [3] and electron number distribution functions (EDF) [4]. In IQA, themolecular energy is exactly written as a sum of atomic or fragment self-energies and interatomic (orinter-fragment) interaction energies. The evolution of self-energies along bonding coordinatesallows for the identification of the proper atomic/fragment state that reflects the actual electronicstate of each fragment in-the-molecule, which can then be used to properly define IBEs. Someresults on methane, ethene, ethyne, dinitrogen, and dicarbon will be shown.
Acknowledgments
We thank the spanish MINECO, grant CTQ2015-65790-P, the FICyT, grant GRUPIN14-049,and the European Union FEDER funds for financial support.
References
[1] S. Shaik, H. S. Rzepa, R. Hoffmann, Angew. Chemie Intl. Ed , 52. (2013) 3020.[2] D. Cremer, A. Wu, A. Larsson, E. Kraka, J. Mol. Model. 6. (2000) 296 [3] M. A. Blanco, A. Martín Pendás, E. Francisco, J. Chem. Theory Comput. 1 (2005) 1096.[4] E. Francisco, A. Martín Pendás, M. A. Blanco, J. Chem. Phys. 126 (2007) 094102
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nº
Simposium Title
Continuous spectrum of the H atom after confinement
M.F. Morcillo1, J.M. Alcaraz-Pelegrina1, A. Sarsa1,*
1 Departamento de Física, Campus de Rabanales, Edif. C2, Universidad de Córdoba, 14017 Córdoba (Spain)
Introduction
The study of confinement effects on atomic and molecular systems has been a topic of recent
interest [1]. Experimentally it has been possible to insert atoms and molecules within molecular
nanocavities. This brings the possibility of employing such as novel structures for different
applications, ranging from energy storage and transport to medical use. In addition, depending on
the relative sizes, confinement may exert a strong influence on the electronic structure of the guest
atom or molecule. This opens up the field for manipulating the spectroscopic properties of the
confined atom, which is of great interest in optics and electronics.
Method
In this work we focus in the stability of the atom after it is released from the cavity. If the
confined atom or molecule is stored in order to be used to produce energy or to be transported, it is
important to analyze if the atom is stable when the confining environment is removed.
Here we consider the H atom within an impenetrable spherical wall. This simple model
reproduces the most important physical features of confinement and the study of the H atom
simplifies the computational problem and the possible excitation mechanisms after the system is
released. The excited states of the H atom, both in the discrete and the continuous spectra can be
obtained very accurately.
We assume that the atom is liberated in a period of time that can be considered small as
compared with the dynamics of the atom. Then the sudden approximation can be employed to study
the state of the atom after confinement is removed. Within this approach, the time dependent state
of the released atom after is expanded in terms of the stationary states of the free Hamiltonian. In
this expansion both, the bound states and the Coulomb wave functions need to be included. The
linear coefficients provide the amplitude probability of the released atom to reach the corresponding
stationary state of the unconfined atom. The values of these coefficients are calculated as the
overlap of the confined wave function with the wave function of the unconfined atom.
Results and discussion
In Table 1 we show the energy of the three stationary states of the H atom here studied. We
consider hard wall spherical confinement of radius 2 au with the nucleus of the atom fixed at the
center of the wall.
Table 1: Energy and ionization probability of the atom when confinement is removed for the three confined states of the H atom here studied.
The confinement radius is 2 au (2.117 A)
Atomic state Energy (eV) Ionization probability
3s 50.958812 0.9644
3p 34.327738 0.9488
3d 16.907951 0.9727
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nº
Simposium Title
In Figure 1 we plot the ionization probability energy distribution of the atom when
confinement is released.
Figure 1: Probability distribution function for the energy of the ionized electron when confinement is removed for the three different states
studied. The confinement radius is 2 au and the energy of the confined states and the total ionization probability is given in Table 1.
In all of the cases shown, a spread distribution around a principal maximum is obtained. The
value of the energy at the maximum is close and smaller thant the energy of the confined state. The
other secondary maxima, obtained at higher energies, are less important. The probability
distribution presents several nodes, showing that no electrons with that value of the energy can be
emitted.
Acknowledgments
Financial support from the Spanish DGICYT and FEDER, project number FIS2015-69941-C2-
2P, and from the Junta de Andalucía (FQM378) and Universidad de Córdoba is gratefully
acknowledged.
References
[1] K. D. Sen (Editor), Electronic structure of quantum confined atoms and molecules, Springer, Switzerland, 2014.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºSimposium Title
Hydrogen Diffusion along SWCNTs: Time-scale Separation and Tunneling
Effects
M. Mondelo-Martell, F. Huarte-Larrañaga*
Department of Material Science and Physical Chemistry & Institute for Theoretical and Computational Chemistry, C/ Martí i Franqués 1, 08028 Barcelona.
Introduction
The role of nanostructured materials in both fundamental and applied research is everincreasing due to their interesting and unique properties, from catalysis to electronics [1,2]. Aspecific field of interest is the understanding and development of storage devices for light gases,specially for energy applications (hydrogen) or environmental reasons (CO2, H2S). Carbonnanotubes have been largely studied with the idea of designing possible storage devices for H2 sincethe late 1990s [3]. However, a complete quantum dynamics description of the diffusion mechanisminside these structures is still lacking.
Here we present a quantum mechanical study of the diffusion of the H2 molecule along a narrow(8,0) Single-walled Carbon Nanotube (SWCNT). Following previous works by our group [4] wehave modelled the system considering all the degrees of freedom (DOFs, internal and translational)of the hydrogen molecule and a rigid nanostructure. The cylindrical shape of the potential energysurface, showing five bound DOFs and one unbound DOF, has prompted us to develop an exactdiabatization formalism separating two sets of weakly coupled degrees of freedom: on one hand, theunbound coordinate corresponding to the motion of the center of mass of H2 along the nanotube’saxis, and in the other the remaining 5 DOFs, which are effectively confined by the nanostructure.By applying a complete separability assumption to the confined and unbound DOFs we have alsodeveloped an adiabatic approximation to the Hamiltonian, which increases the algorithm efficiencywhile maintaining the accuracy of the results. Both approaches have been employed to simulateHydrogen diffusion along the SWCNT at temperatures in the 45-135 K range. The computationaladvantages provided by both method have enabled us to propagate the wave function beyond 15picoseconds using the State Averaged - MCTDH [5] code, revealing a remarkable resonant structureas well as a noticeable tunnelling effect.
Figure 1 Illustration: H2 entering the nanotube and diffusion rates calculated in the present work
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºSimposium Title
Figure 2 Calculated diffusion rates for H2 along an (8,0) carbon nanotube using the diabatic (solid line) and adiabatic (dashed) approaches. Gray markers correspond to the experimental H2 diffusion data in a Carbon Molecular Sieve obtained from Ref. [6].
Acknowledgments
Financial support from the Spanish Ministerio de Economia y Competitividad (CTQ2013-41307-P) and Generalitat de Catalunya (2014- SGR-25) is acknowledged. M.M.-M. further thanks apre-doctoral grant from the FPU program (FPU2013/02210) from the Spanish Ministerio deEducacion, Cultura y Deporte.
References
[1] G. E. Ioannatos and X. E. Verykios, Int. J. Hydrogen Energy 35, 622 (2010).[2] X. Ren, C. Chen, M. Nagatsu, and X. Wang, Chem. Eng. J. 170, 395 (2011).[3] A. C. Dillon, K. M. Jones, T. a. Bekkedahl, C. H. Kiang, D. S. Bethune, and M. J. Heben, Nature 386, 6623 (1997).[4] M. Mondelo-Martell and F. Huarte-Larrañaga, Chem. Phys. 462, 41 (2015).[5] U. Manthe, J. Chem. Phys. 128, 6 (2008).[6] T. X. Nguyen, H. Jobic, S. K. Bhatia, Phys. Rev. Lett. 105 085901 (2010).
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nº 1Simposium Title: Molecular Physics at the Edge
Quantum Nuclear Motion of Helium and Molecular Nitrogen
Clusters in Carbon Nanotubes
A. W. Hauser1, A. O. Mitrushchenkov2, M. P. de Lara-Castells3,* 1 Graz University of Technology, Institute of Experimental Physics, Petersgasse 16, 8010 Graz, Austria2 Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée, France3 Instituto de F sica Fundamental (C.S.I.C.), Serrano 123, E-28006 Madrid, Spainı ı
* corresponding author e-mail
Introduction
High-surface areas and precisely tuned pores of carbon nanotubes make them relevantmaterials for applications such as in gas adsorption, selective separation of light isotopes, andnanoreactors for quasi one-dimensional confinement of metal nanoparticles. Understanding the roleof quantum nuclear effects and intramolecular interactions in the motion of molecules in carbonnanotubes is deeply fundamental. Very recent experimental measurements at low temperatures (2-5K) of Ohba [1] revealed that much more molecules of nitrogen than helium atoms absorb in smalldiameter (below 0.7 nm) carbon nanopores, despite of the larger kinetic diameter of the former.
Using the helium density-functional formulation for a large 4He droplet containing a carbonnanotubes inside, we first show that the experiment can be understood by considering very largezero-point effects in the helium motion, which includes the formation of cavities with zero heliumdensities [2]. Second, we present an ad-hoc developed nuclear wave-function treatment to provide adetailed insight into the effects of quantum confinement for both N 2 and 4He clusters in carbonnanotubes as a function of the tube diameter [3]. Third, we describe our novel pairwise potentialmodel [3] describing the gas adsorption to carbon materials which relies on DFT-based symmetry-adapted perturbation theory. Finally, we propose an embedding approach combining nuclear densityfunctional and wave-function treatments [3].
Acknowledgments
This work has been partly supported by the COST Action CM1405 ``Molecules in Motion"(MOLIM) and MICINN (Spain) under Grant No. MAT2016-75354-P.
References
[1] Ohba , Sci. Rep. 6 (2016) 28992.[2] A. W. Hauser and M. P. de Lara-Castells, . J. Phys. Chem. Lett. 7 (2016) 4929.[3] A. W. Hauser, A. O. Mitrushchenkov, M. P. de Lara-Castells, . J. Phys. Chem. C 121 (2017) 3807.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºMolecular Physics at the Edge
Experimental characterization of the basic intermolecular interaction
components
Fernando Pirani1
1 Dipartimento di Chimica, Biologia e Biotecnologie,, Università di Perugia, 06123 Perugia, Italy, and Istituto di Nanotecnologia (CNR NANOTEC) , 70126 Bari, Italy
The target of the present work is the detailed characterization of the most relevant componentsof the intermolecular interaction, which control the molecular dynamics under a variety ofconditions. To this purpose, molecular beam experiments have been performed under conditionsproper to isolate quantum effects in the single collision events, which probe in detail the projectile-target interaction. Particular attention is addressed to range, strength and anisotropy of non-covalentinteraction components, due to the balance of size (or Pauli) repulsion with dispersion and inductionattraction, to which must be added electrostatic contributions, and of other components of covalent(chemical) nature, mostly affected by charge (electron) transfer effects. The analysis of severalexperimental findings has been important to develop suitable analytical representations of thepotential energy surfaces (PESs), tested and improved by exploiting also the comparison withresults of ab initio calculations, useful to provide an internally consistent description of theintermolecular interaction both in the most and less stable configurations of the interacting system.The proper formulation of the PESs is crucial not only to describe the dynamics of elementaryprocesses occurring in interstellar medium and in planetary atmospheres, but also to controlequilibrium a non-equilibrium phenomena of applied interest, as those occurring in combustion,flames and plasmas.
Acknowledgments
The financial support of this research is from the “Fondazione Cassa di Risparmio di Perugia”(Contract No. 2015.0331.021) and from the “Dipartimento di Chimica, Biologia e Biotecnologie,Università di Perugia”
XXXVI Biannual Meeting of the Real Sociedad Española de Física page nº 1 Symposium Title: Molecular Physics at the Edge
Ultrafast broadband transient absorption spectroscopy of a single molecule
Matz Liebel1, Costanza Toninelli2 and Niek F. van Hulst1,3 1 ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels, Barcelona 2 CNR-INO, Istituto Nazionale di Ottica, LENS Via Carrara 1, Sesto Fiorentino (FI) 50019, Italy 3 ICREA-Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona
* [email protected]; [email protected]
Introduction
We present the first ultrafast transient absorption of a single molecule. Specifically, we trace the femtosecond evolution of excited electronic state spectra of single molecules over hundreds of nanometers of bandwidth at room temperature. The non-linear ultrafast response of the single molecule is probed using a broadband laser in an effective 3-pulse scheme with fluorescence detection. A first excitation pulse is followed by a phase-locked de-excitation pulse-pair, providing spectral encoding while preserving 25 fs temporal resolution. This experimental realization of true single molecule transient absorption spectroscopy demonstrates that two-dimensional electronic spectroscopy of single molecules is experimentally in reach [1].
Discussion
In this presentation we will show the first transient stimulated emission spectrum of a single molecule as well as the first direct observation of the dynamical evolution of such a spectrum on an ultrafast (<30 fs) timescale in condensed phase at room temperature [1]. We attribute the resolved spectro-temporal dynamics to a combination of Stokes shift as well as vibrational relaxation. The new methodology relies on precise encoding of spectral information at a well-defined pump-probe time-delay and next retrieval of this information by means of fluorescence at a much later point in time. A combination of amplitude only pulse shaping with concepts borrowed from NMR spectroscopy allows to convert the encoded information into an excited state emission spectrum at the respective time-delay while, simultaneously, keeping the temporal resolution of the experiment close to the transform limit. The spectral encoding approach allows to access molecular dynamics of single molecules within the first few tens of femtoseconds after photoexcitation. Even conventional transient absorption experiments, performed at the ensemble level, struggle to access the 10s of femtoseconds time scale due to nonlinear signals being generated by the temporally overlapping pump and probe pulses. At the single molecule level, advantageously, it is possible to circumvent this limitation. The signal arising from the single molecule itself shows a distinctly different spatial emission pattern as
Figure 1. (a) Experimental implementation of a single molecule transient absorption experiment and representative images of a single DBT molecule and its single-step bleaching event. (b) Concept of spectral measurements by spectral amplitude modulation, mimicking the spectral control obtained from a phase-locked pulse-pair. (c) Fluorescence traces recorded by pure spectral modulation of the excitation pulse for individual single DBT molecules (orange) as well as the averaged signal (blue). (d) Fluorescence excitation spectra obtained from (c) as the real part of the fast Fourier transformation of the respective fluorescence traces for the individual molecules (orange) and the average of all traces (blue). An ensemble absorption spectrum of DBT dissolved in Toluene (dashed line) is shown for comparison. The white area indicates the spectral window of the excitation pulse [1].
XXXVI Biannual Meeting of the Real Sociedad Española de Física page nº 2 Symposium Title: Molecular Physics at the Edge
compared to all nonlinear signals generated in the sample matrix (or support) and a simple dark-field mask in the back-focal-plane of the collection objective efficiently eliminates their contributions. This notion is further supported by the complete absence of spectral amplitude for the experiment performed after photobleaching. The transient ultrafast encoded single molecule spectroscopy (trueSMS) presented here is conceptually almost identical to fluorescence detected 2D electronic spectroscopy albeit the latter two field contributions not being physically separated. Both ground and excited electronic states can be addressed by the spectral shaping, and 2D information retrieved when combined with advanced signal acquisition as for example the concept of compressed sensing. We therefore believe that the initial steps presented here will ultimately enable 2D trueSMS spectroscopy for single emitters such as quantum dots, plasmonic structures and ultimately single molecules.
Acknowledgments
This research is funded by the European Commission (ERC Adv. Grant 670949-LightNet); MINECO Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-0522), FIS2015-69258-P; Catalan AGAUR (2014 SGR01540); CERCA Programme of Generalitat de Catalunya; and Fundació CELLEX (Barcelona). M.L. acknowledges financial support from the Marie-Curie International Fellowship COFUND.
References
[1] Matz Liebel, Costanza Toninelli and Niek F. van Hulst, Paper submitted, under review.
Figure 2. Schematic of a typical time resolved pump-probe experiment and signal considerations due to the diffraction limit for a possible single molecule implementation (left). Experimental implementation of the broadband single molecule transient absorption experiment relying on fluorescence detection (right). The spectro-temporal dynamics of the excited electronic state are obtained by spectrally modulating (encoding) the probe pulse in order to modify the resulting fluorescence signal [1].
XXXVI Reunión Bienal de la Real Sociedad Española de Física Título Simposio
Laboratory study of inelastic collisions of O2 with He at low temperature
F. Gámez1,2, E. Moreno1,3, G. Tejeda1, M. I. Hernández4, S. Montero1, J. M. Fernández1,* 1Instituto de Estructura de la Materia CSIC, Serrano 121, 28006 Madrid, Spain 2Universidad Pablo de Olavide, Ctra. Utrera km 1, 41013, Seville, Spain 3Instituto de Ciencia de Materiales, CSIC, Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain 4Instituto de Física Fundamental CSIC, Serrano 123, 28006 Madrid, Spain
* e-mail: [email protected]
Abstract
State-to-state rate coefficients for the inelastic collisions of O2 with He at low temperature are investigated by means of an experimental procedure based on supersonic gas jets probed by Raman spectroscopy. The procedure employs a kinetic master equation (MEQ) which describes the time evolution of the rotational populations of O2 along three supersonic jets of O2 + He mixtures. The MEQ is expressed in terms of experimental quantities (number density and rotational populations), and calculated rate coefficients for the O2:He and O2:O2 inelastic collisions from the literature. By scaling these rate coefficients, a satisfactory agreement with the experiments is accomplished for temperatures between 10 and 34 K.
Communication
Inelastic nonreactive collisions between molecules are responsible for many phenomena in gases, like the transport properties [1], the broadening of spectral lines [2], and rotational and vibrational excite-relaxation [3], and play an important role in the out-of-equilibrium environment of supersonic gas jets [4,5]. As such, they are of fundamental interest in molecular quantum dynamics, and of practical interest in aeronautics, atmospheric physics, and astrophysics [6].
Molecular oxygen O2 is an important component of Earth's atmosphere, and it has been detected also in the interstellar medium [7]. There is much interest in Astrophysics on inelastic collisions of small molecules with He and H2, the predominant collision partners in molecular clouds [6], because much information about such regions comes from emission lines due to rotationally excited molecules. On the other hand, O2:He collisions are also crucial to produce cold and ultracold O2 molecules [8].
State-to-state cross sections and rate coefficients for scattering of He by O2 molecules have been calculated by Lique [9]. From the experimental point of view, inelastic collisions of O2 with He atoms have been studied previously [10-12] in molecular beam experiments, and qualitatively compared with the calculations. However, for practical modelling of interstellar gas regions under non local equilibrium conditions, a set of absolute state-to-state rate coefficients (sts-rates in short), validated by quantitative experiment, is needed.
In the last years, we have developed [13] an original experimental methodology to study rotationally inelastic collisions of small molecules in their vibrational ground state, at very low temperature (<50 K). The method can provide quantitative assessment of sts-rates calculated from first principles. So far, it has been applied to para- and ortho-H2 [14,15], N2 [16,17], and their collisions with He [18,19], as well as O2:O2 [20] and H2O:He [21] collisions.
The experimental setup and methodology developed in our laboratory will be described first. The procedure is based on tracking the time evolution of the rotational population along supersonic gas jets by Raman spectroscopy. Then, experimental results for three supersonic jets of O2 + He mixtures, with O2 mole fractions 0.025, 0.11 and 0.47, will be shown. Rotational populations, PN (where N is the rotational quantum number), and number densities, n, can be measured along the jet axis z with time resolution of nanoseconds. The number densities n(z) were measured from the integrated Raman intensity of the Q-branch of the O2 vibrational band at 1555 cm−1. The rotational populations PN(z) were determined from the summed Raman intensities over the triplets associated with the N→N+2 rotational transitions. To a good approximation, the measured rotational
XXXVI Reunión Bienal de la Real Sociedad Española de Física Título Simposio
populations PN obey (up to N=9) a Boltzmann distribution at a rotational temperature TR. In turn, the translational temperature TT has been determined from the isentropic condition along the jet.
As a result of the inelastic collisions within a bath of He atoms at a translational temperature TT, the time evolution of the population PN of a rotational state N of an O2 molecule in the supersonic jet obeys the Master Equation (MEQ)
→ℓ ℓ ℓ→
ℓ
where →ℓ are the state-to-state rate coefficients, which are a function of the translational temperature TT . The left-hand-side (LHS) of the MEQ is an experimental quantity, while the right-hand-side (RHS) is a linear combination of the sts-rates, with coefficients determined by the experiment (n and PN). The sum of squared residual difference (LHS-RHS)2 has been minimized by scaling the sts-rates from theoretical calculations [9]. This way, a set of sts-rates scaled to the experiment have been obtained, which reproduce the experiments within 20% on average.
This work has been supported by the Spanish Ministerio de Economía y Competitividad
(MINECO), grants FIS2013-48275-C2 and CONSOLIDER-ASTROMOL CSD2009-0038. F.G. thanks the Spanish Regional Government of Andalucía for a postdoctoral grant (project P07-FQM-2600).
References
[1] C. S. Wang-Chang, G. E. Uhlenbeck, and J. deBoer, in Studies in Statistical Mechanics, vol. 2, North-Holland, Amsterdam, 1964. [2] J. M. Hartmann, C. Boulet, and D. Robert, Collisional Effects on Molecular Spectra, Elsevier, Amsterdam, 2008. [3] J. D. Lambert, Vibrational and Rotational Relaxation in Gases, Clarendon Press, Oxford, 1977. [4] D. R. Miller, “Free Jet Sources”, in G. Scoles (Ed.), Atomic and Molecular Beam Methods, Oxford University Press, 1988, Volume 1. [5] S. Montero, B. Maté, G. Tejeda, J. M. Fernández and A. Ramos, “Raman Studies of Free Jet Expansion”, in R. Campargue (Ed.), Atomic and Molecular Beams. The State of the Art 2000, Springer Verlag, Berlin, 2001, pp 295–306. [6] D. Flower, Molecular Collisions in the Interstellar Medium, Cambridge U. Press, 2003. [7] B. Larsson et al. Astron. Astrophys., 466 (2007) 999. [8] N. Balakrishnan and A. Dalgarno, J. Phys. Chem. A 105 (2001) 2348. [9] F. Lique, J. Chem. Phys. 132 (2010) 044311. [10] V. Aquilanti, D. Ascenzi, D. Cappelletti, and F. Pirani, Nature, 371 (1994) 399. [11] D. Patterson and J. M. Doyle, J. Chem. Phys. 126 (2007) 154307. [12] C. K. Bishwakarma, G. van Oevelen, R. Scheidsbach, D. H Parker, Y. Kalugina, and F. Lique, J. Phys. Chem. A 120 (2016) 868. [13] J. M. Fernández, J. P. Fonfría, A. Ramos, G. Tejeda, S. Montero, and F. Thibault, “Inelastic collisions of N2, H2, and H2+He mixtures in supersonic jets by Raman spectroscopy”, in T. Abe (Ed.) RAREFIED GAS DYNAMICS, AIP Conference Proceedings #1084 (2009), pp 571--576. [14] B. Maté, F. Thibault, G. Tejeda, J. M. Fernández, and S. Montero, J. Chem. Phys. 122 (2005) 064313. [15] S. Montero, F. Thibault, G. Tejeda, and J. M. Fernández, J. Chem. Phys., 125 (2006) 124301. [16] A. Ramos, G. Tejeda, J. M. Fernández, and S. Montero, Phys. Rev. A., 66 (2002) 022702. [17] J. P. Fonfría, A. Ramos, F. Thibault, G. Tejeda, J. M. Fernández, and S. Montero, J. Chem. Phys. 127 (2007) 134305. [18] B. Maté, F. Thibault, A. Ramos, G. Tejeda, J. M. Fernández, and S. Montero, J. Chem. Phys. 118 (2003) 4477. [19] G. Tejeda, F. Thibault, J. M. Fernández, and S. Montero, J. Chem. Phys. 128 (2008) 224308. [20] J. Pérez-Ríos, G. Tejeda, J. M. Fernández, M. I. Hernández, and S. Montero, J. Chem. Phys. 134 (2011) 174307. [21] G. Tejeda, E. Carmona-Novillo, E. Moreno, J. M. Fernández, M. I. Hernández, and S. Montero, Astrophys. J. Suppl. Ser. 216 (2015) 3.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºSimposium Title
Acid dissociation in microsolvated environments
R. Pérez de Tudela1,*, D. Marx1
1 Lehrstuhl für Theoretische Chemie, NC 03/52, Ruhr-Universität Bochum, 44780 Bochum, Germany
The long-standing and fundamental question regarding the minimumnumber of water molecules required to dissociate an acid molecule in anaqueous microsolvation environment still remains open. For HClinteracting with water molecules - one added after the other - there isconvincing evidence that an ion pair, and thus the dissociated acidmolecule, can be stabilized using a minimum number of only four watermolecules (see Fig. 1) [1,2]. However, this number has been questionedboth on the experimental [3–6] and the theoretical sides [7]. In thisrespect, an experiment appeared recently in the literature [8] whichsuggested a new approach. In this experiment the dipole moment ofHCl•(H2O)n clusters was measured as a function of the number of watermolecules (see Fig. 2). The key result of those measurements was anoticeable rise of the total dipole moment of these clusters when n=6. Atempting explanation was to assign this sudden rise in the dipole momentto the dissociation of the HCl molecule.
In this work, ab initio pathintegral calculations wereperformed in order to try todisentangle the controversy ofwhether it is 4 or 6 watermolecules the minimum required to dissociate the chloridricacid. Our results show that measuring the dipole moment ofHCl•(H2O)n clusters does not give any information about thedissociative state of the HCl molecule. In addition, a detailedanalysis of thermal and quantum effects provides a muchclearer picture of the acid dissociation process inmicrosolvated environments.
The Cluster of Excellence “RESOLV” (EXC 1069) funded by the DeutscheForschungsgemeinschaft (DFG) is gratefully acknowledged along with computer time supportfrom HPC-RESOLV, HPC@ZEMOS, BOVILAB@RUB and RV-NRW.
References
[1] A. Gutberlet, G. Schwaab, Ö. Birer, M. Masia, A. Kaczmarek, H. Forbert, M. Havenith, D. Marx, Science 324(2009) 1545.[2] H. Forbert, M. Masia, A. Kaczmarek-Kedziera, N. N. Nair, D. Marx, J. Am. Chem. Soc. 133, (2011) 4062.[3] D. Skvortsov, S. J. Lee, M. Y. Choi, and A. F. Vilesov, J. Phys. Chem. A 113, (2009) 7360 .[4] S. D. Flynn, D. Skvortsov, A. M. Morrison, T. Liang, M. Y. Choi, G. E. Douberly, A. F.Vilesov, J. Phys. Chem. Lett. 1 (2010) 2233.[5] A. M. Morrison, S. D. Flynn, T. Liang, G. E. Douberly, J. Phys. Chem. A 114 (2010) 8090.[6] M. Letzner, S. Gruen, D. Habig, K. Hanke, T. Endres, P. Nieto, G. Schwaab, L. Walewski,M. Wollenhaupt, H. Forbert, D. Marx, M. Havenith, J. Chem. Phys. 139 (2013) 154304.[7] A. Vargas-Caamal, J. L. Cabellos, F. Ortiz-Chi, H. S. Rzepa, A. Restrepo, G. Merino, Chem. Eur. J. 22 (2016) 2812.[8] N. Guggemos, P. Slavíček, V. V. Kresin, Phys. Rev. Lett. 114 (2015) 043401.
Figure 1: IR depletion spectra ofthe symmetric hydronium stretchof H3O+(H2O)3Cl- in helium nanodroplets.
Figure 2: Electric dipole moment of pure (bottom) and HCl-doped (top) water clusters
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nº
Simposium Title
Hybrid Organic-Inorganic Halide Perovskites for Photovoltaics and Lasing
Applications: Insights from First Principles Calculations
G. Giorgi 1, *
1 Department of Civil and Environmental Engineering (DICA), The University of Perugia, Via G. Duranti 93, I-06125 Perugia, Italy
Bulk organic-inorganic halide perovskites (OIHPs) are compounds characterized by the chemical
formula AMX3 (A=organic cation; M=Ge, Sn, Pb; X=halide) whose hybrid nature is conferred by the
presence of an organic cation (the barrier [1]) that fits the inorganic semiconductor network cavities
according to well established tolerance size parameters [2].
The scientific community has recently renewed its interest towards 3D OIHPs (2D OIHP class was
initially investigated two decades ago for optoelectronics applications [3]) because of the superior
features as light harvesters in photovoltaic (PV) devices due to their manifold unique properties [4].
Researchers in Miyasaka’s Lab have at first assembled OIHP based solar cells [5] with
photoconversion efficiencies (PCEs) of ~3.5%. Thereafter, impressive improvements have been
achieved with the current best devices characterized by certified PCE > 22% [6]. Methylammonium
lead iodide (MAPbI3, MA=+CH3NH3) is the most widely employed OIHP due to its high
compatibility with solution-based processing, the high absorption coefficient, and its bandgap close
to the optimal one for single junction solar cells. There is anyway scientific evidence of excellent
solar cells also based on OIHPs with different cations, both in the A- and in the B- site [7] (see Fig.
1).
It is interesting to stress that while 3D bulk OIHP bulk properties are receiving deep attention, there
is total lack of knowledge of the chemico-physical properties of OIHP clusters (0D, see Fig. 2) and
quantum dots. This is surprising in view of their possible application not only in PV but also in lasing
and as quantum emitters [8].
Figure 1. Top view of the 3D guanidinium lead iodide (GAPbI3, GA=+C(NH2)3).(Reprinted from Ref [7(b)], ACS Editors' Choice]
In the first part of the contribution I will provide an overview of the structural, electronic, and optical
properties of bulk OIHPs; the second part will, at variance, mainly focus on results concerning 0D
OIHP with particular attention to the possible analogies and differences with the 3D counterpart.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nº
Simposium Title
Figure 2. MAPbI3 clusters of increasing size. (Reprinted with permission from Ref. [8(c)].Copyright 2016. American Chemical Society.)
References
[1] G. C. Papavassiliou, Prog. Solid. State Chem. 12 (1979) 185.
[2] (a) V. M. Goldschmidt, Naturwissenschaften, 14 (1926) 477; (b) G. Kieslich, S. Sun, A. K. Cheetham, Chem. Sci. 5,
(2014) 4712; (c) ibid. 6 (2015) 3430.
[3] (a) D. B.Mitzi, S. Wang, C. A. Feild, C. A. Chess, A. M. Guloy, Science 267 (1995) 1473; (b) D. B. Mitzi, Inorg.
Chem. 39 (2000) 6107.
[4] (a) J. H. Heo, S. H. Im, J. H. Noh, T. N. Mandal, C.-S. Lim, J. A. Chang, Y. H. Lee, H.-j. Kim, A. Sarkar, Md. K.
Nazeeruddin, M. Grätzel, S. I. Seok, Nat. Photon. 7 (2013) 486; (b) L. Etgar, P. Gao, Z. Xue, Q. Peng, A. K. Chandiran,
B. Liu, Md. K. Nazeeruddin, M. Gratzel, J. Am. Chem. Soc. 134 (2012) 17396; (c) W. A. Laban, L. Etgar, Energy Environ.
Sci. 6 (2013) 3249; (d) M. M. Lee, J. Teuscher, T. Miyasaka, T. N. Murakami, H. J. Snaith, Science 338 (2012) 643; (e)
G. Giorgi J.-I. Fujisawa, H. Segawa, K. Yamashita, J. Phys. Chem. Lett. 4 (2013) 4213; (f) G. Xing, N. Mathews, S. Sun,
S. S. Lim, Y. M. Lam, M. Grätzel, S. Mhaisalkar, T. C. Sum, Science 342 (2013) 344; (g) S. D. Stranks, G. E. Eperon, G.
Grancini, C. Menelaou, M. J. P. Alcocer, T. Leijtens, L. M. Herz, A. Petrozza, H. J. Snaith, Science 342 (2013) 341.
[5] A. Kojima, K. Teshima, Y. Shirai, T. Miyasaka, J. Am. Chem. Soc. 131 (2009) 6050.
[6] http://www.nrel.gov/ncpv/images/efficiency_chart.jpg
[7] (a) A. Amat, E. Mosconi, E. Ronca, C. Quarti, P. Umari, Md. K. Nazeeruddin, M. Gratzel, F. De Angelis, Nano Lett.
14 (2014) 3608; (b) G. Giorgi J.-I. Fujisawa, H. Segawa, K. Yamashita, J. Phys. Chem. C 119 (2015) 4694, ACS Editors'
Choice http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.5b00051 ; (c) G. Giorgi, K. Yamashita, Nanotechnology 26 (2015)
442001; (d) G. Giorgi, K. Yamashita, Chem. Lett. 44 (2015) 826.
[8] (a) L. C. Schmidt, A. Pertegas, S. Gonzalez-Carrero, O. Malinkiewicz, S. Agouram, G. Minguez Espallargas, H. J.
Bolink, R. E. Galian, J. Perez-Prieto, J. Am. Chem. Soc. 136 (2014) 850. (b) M. F. Aygüler, M. D. Weber, B. M. D.
Puscher, D. D. Medina, P. Docampo, R. D. Costa, J. Phys. Chem. C 119 (2015) 12047. (c) G. Giorgi, K. Yamashita, J.
Phys. Chem. Lett. 7 (2016) 888; (d) G. Giorgi, T. Yoshihara, K. Yamashita, Phys. Chem. Chem. Phys. 18 (2016) 27124.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºSimposium Title
Revealing the low-energy landscape of clusters: from the solvation of ions to the
self-assembling of colloidal particles
J.M.C. Marques1,*
1 CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
Introduction
Knowledge about the structure that different types of matter may acquire is fundamental tounderstand several properties emerging around in Nature and to build up new materials. Suchstructural organization can be observed at different scales, ranging from aggregates of atoms in thegas-phase to colloids in condensed-matter physics. From the theoretical view point, one has tomodel the interactions among the particles of the system (e.g., atoms or molecules) and, then, applyoptimization techniques. In general, this is a very difficult task that requires the application of state-of-the-art optimization methods. Over the past decade or so, we have developed evolutionaryalgorithms (EAs) that has been able to discover putative global minima for various cluster systems,including atomic [1-3], molecular [4] and colloidal [5,6] clusters.
In this talk, we will present the main ingredients of our EA and its application to the solvationof ions [7,8] as well as to the study of self-assembling phenomena in colloidal systems [6,9,10]. Inparticular, we will focus on the study of alkali-ions solvation (Figure 1) and the formation ofaggregates of charged colloidal particles (Figure 2). The analysis of the energetics and structure ofthe clusters relies on the features of the potential functions employed for modeling the interactionsamong the particles.
Figures
Figure 1: Li+Arn clusters modelled with model
potentials that include only 2-body (right), and
both 2- and 3-body interactions (left).
Figure 2: Low-energy structures of
charged colloidal clusters modelled with
an attractive short-range Morse potential
and a repulsive Yukawa function.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºSimposium Title
Acknowledgments
We acknowledge the support from the Coimbra Chemistry Center (CQC), which is financed bythe Portuguese “Fundação para a Ciência e a Tecnologia” (FCT) through the Project No 007630UID/QUI/00313/2013, co-funded by COMPETE2020-UE. We also acknowledge the FCT/CAPESbilateral Project (Ref: 2984/DRI and 88887.125439/2016-00/CAPES).
References
[1] F.B. Pereira, J.M.C. Marques, T. Leitão, J. Tavares, “Designing efficient evolutionary algorithms for clusteroptimization: a study on locality”, in: P. Siarry, Z. Michalewicz (Eds.), Advances in Metaheuristics for HardOptimization (Springer Natural Computing Series), Springer, Berlin, 2008, pp. 223-250. [2] F.B. Pereira, J.M.C. Marques, Evol. Intel. 2 (2009) 121.[3] J.M.C. Marques, F.B. Pereira, Chem. Phys. Lett. 485 (2010) 211.[4] J.L. Llanio-Trujillo, J.M.C. Marques, F.B. Pereira, J. Phys. Chem. A 115 (2011) 2130.[5] J.M.C. Marques, F.B. Pereira, J. Mol. Liq. 210 (2015) 51.[6] S.M.A. Cruz, J.M.C. Marques, F.B. Pereira, J. Chem. Phys. 145 (2016) 154109.[7] J.M.C. Marques, F.B. Pereira, J.L. Llanio-Trujillo, P.E. Abreu, M. Albertí, A. Aguilar, F. Pirani, M. Bartolomei, Phil.Trans. R. Soc. A 375 (2017) 20160198.[8] F.V. Prudente, J.M.C. Marques, F.B. Pereira, in preparation.[9] S.M.A. Cruz, J.M.C. Marques, J. Phys. Chem. B 120 (2016) 3455.[10] S.M.A. Cruz, J.M.C. Marques, Comput. Theor. Chem. 1107 (2017) 82.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºSimposium Title Molecular physics at the edge
Coarse-graining polycyclic aromatic hydrocarbon clusters
J. Hernández-Rojas1*, F. Calvo2, D. J. Wales3 1 Departamento de Física and IUdEA, Universidad de La Laguna, 38205, La Laguna, Tenerife, Spain.2 LiPHY, Université Grenoble Alpes and CNRS, 140 Av. de la physique, 38402 St Martin d'Hères, France.3 Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
* corresponding author e-mail: [email protected]
In this talk we present a coarse-grained model based on the Paramonov-Yaliraki (PY) potential [1] for modeling interacting polycyclic aromatic hydrocarbon (PAH) molecules [2]. This model is parameterized using all-atom reference data to study coronene (C24H12), circumcoronene (C54H18) and their aggregates. We show the ability of the coarse-grained approach to reproduce the global minima predicted by the all-atom potential for clusters containing up to 20 molecules. One-dimensional columnar motifs are found to be most favourable in small clusters with mixed stacks in larger clusters. Dynamical and thermodynamical properties of the coronene octamer are discussed in the energy landscapes framework [3]. From a connected database of stationary points of the potential energy surface and using the harmonic normal mode approximation, we show the potential and free energy landscapes and relevant rearrangement pathways between competing motifs, as determined using discrete path sampling [4], which exhibit highly cooperative motion [5].
J. H.-R. acknowledges financial support from Ministerio de Economía y Competividad under Grants No. FIS2013-41532-P and FIS2016-79596-P.
References
[1] L. Paramonov, S. N. Yaliraki, J. Chem. Phys. 123 (2005) 194111.[2] J. Hernández-Rojas, F. Calvo, D. J. Wales, Phys. Chem. Chem. Phys. 18 (2016) 13736.[3] D. J. Wales, Energy Landscapes, Cambridge University Press, Cambridge, 2003.[4] D. J. Wales, Mol. Phys. 100 (2002) 3285. [5] J. Hernández-Rojas, F. Calvo, S. Niblett, D. J. Wales, Phys. Chem. Chem. Phys. 19 (2017) 1884.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nº Simposium Title
Experimental and simulation studies of the stepped adsorption of gases
on silicalite-2
E. G. Noya1,*, V. Sánchez-Gil1, J. M. Guil1, E. Lomba1, S. Khatib1,2, A. Sanz1,3, R. Marguta1, L. Pusztai4, L.
Temleitner4, I. da Silva5 and S. Valencia6 1 Instituto de Química-Física Rocasolano, Consejo Superior de Investigaciones Científicas, CSIC, Calle Serrano 119, 28006 Madrid 2 Department of Chemical Engineering, Texas Tech University, Texas, USA 3 NRF centre ``Glass and Time'', IMFUFA, Department of Sciences, Roskilde University, Postbox 260, DK-4000 Roskilde, Denmark 4 Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, P.O. Box 49, H-1525 Budapest, Hungary 5 ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, UK 6 Instituto de Tecnología Química (UPV-CSIC), Avda. de los Naranjos s/n, E-46022 Valencia, Spain
Introduction
Zeolites are materials with a well-defined microporous geometry which make them attractive for many industrial applications, for example, in catalysis or in the separation of mixtures. Understanding their adsorption behaviour is therefore an issue of major relevance from a practical point of view, but also from a fundamental one, as it is common that the properties of the adsorbed fluid are different from those in the bulk. One intriguing finding in this context is the observation that the adsorption isotherm of some simple gases (such as argon) on silicalite-1 exhibits a sub-step at intermediate loadings whereas others (such as methane) do not. Even though considerable experimental and theoretical efforts have been made, the origin of this sub-step is not clear. Some authors claim that this behaviour is a result of a fluid-like to solid-like transition of the adsorbed fluid, whereas others attribute it to a zeolite structural change.
Communication Main Body
With the aim of providing more information that may aid to understand the appearance of sub-steps in the adsorption of some gases in silicalite-1, we have carried out a comprehensive experimental and simulation study of the adsorption of argon and toluene on the structurally similar zeolite silicalite-2. Both zeolites exhibit a similar structure consisting on a three-dimensional network of fairly narrow cylindrical channels with diameters in the range of 5.0 to 5.6 Å. The essential difference lies in the fact that silicalite-1 consists of an array of parallel cylindrical pores intersected by sinusoidal channels, whereas in silicalite-2 all the pores are linear (see Figure 1).
First we performed volumetric experiments that confirm that the adsorption of argon and toluene on silicalite-2 also exhibits a sub-step at half loading (see Figure 2), suggesting that this behaviour
Figure 1. Structure of a) silicalite-2 and b) silicalite-1. Two different views are shown for silicalite-1.
b)a)
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nº Simposium Title
does not depend on the specific structural details of the pores. Subsequently, the microscopic origin of this sub-step was investigated by means of molecular simulations. However, the agreement between the experimental and simulated adsorption isotherm was only qualitative, evidencing deficiencies of the models used to describe the interactions between the different components in the system.
Thus the structure of the adsorbate/adsorbent system was further investigated by performing powder diffraction experiments at three different loads: empty, at half-load (before the sub-step) and at high load (after the sub-step). These data were used as input of N-Reverse Monte Carlo simulations to obtain atomic structural models compatible with the experimental diffractograms. In both instances, namely adsorption of argon and toluene, a good fit of the experimental data was only obtained when incorporating the zeolite flexibility, which shows that the structure of the zeolite can change at high loads or when the size of the adsorbed molecules is comparable to that of the pores. In the case of argon, after the sub-step, a considerable order of the fluid also builds up, suggesting that the sub-step might be attributed to a fluid structural change facilitated by a slight deformation of the zeolite.
Interestingly, the structural models obtained from Monte Carlo and N-Reverse Monte Carlo simulations are significantly different, even at half loading. We ascribe these discrepancies to deficiencies in the adsorbent-adsorbate interatomic potential.
Acknowledgments
This work was funded by Dirección General de Investigación Científica y Técnica under Grants No. FIS2013-47350-C5-4-R, MAT2012-38567-C02-01 and Severo Ochoa SEV-2012-0267. VSG also thanks the CSIC for support by means of a JAE program Ph.D. fellowship.
References
[1] P.L. Llewellyn, et al., Langmuir 9 (1998) 1846. [2] V. Sánchez-Gil et al.; Micropor. Mesopor. Mat. 220 (2016) 218; J. Phys. Chem C 120 (2016) 2260; J. Phys. Chem. C 120 (2016) 8640. [3] V. Sánchez-Gil, E.G. Noya and E. Lomba, J. Chem. Phys. 140 (2014) 024504. [4] E. García-Pérez et al., J. Phys. Chem. C 112 (2008) 9976.
Figure 2. Experimental adsorption isotherms of argon and toluene on silicalite-2.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºSimposium Title
Computational study of mixtures of ILs and alcohols under nanoconfinement
conditions
J.M. Otero-Mato 1, H. Montes-Campos1, L.J. Gallego1, E. López-Lago1, O. Cabeza2, L.M. Varela1,*
1 Grupo de Nanomateriais, Fotónica e Materia Branda, Departamentos de Física de Partículas e de Física Aplicada, Universidade de Santiago de Compostela, Campus Vida s/n E-15782, Santiago de Compostela, Spain2Departamento de Física, Facultade de Ciencias, Universidade da Coruña, Campus A Zapateira s/n, E-15071 A Coruña, Spain
Abstract
Mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] ionic liquid withmolecular amphiphilic solvents, methanol and ethanol under nanoconfinement between neutral andcharged graphene walls are studied in this work by means of molecular dynamics simulations. Theadsorption of alcohol molecules in the walls as well as their distribution in the directions normaland parallel to the interface are studied. The results of these simulations are compared with resultsof the pure IL and its mixtures with water, which were previously reported in ref. [1].
All the results suggest that alcohols distribute quite uniformly throughout the box, being almosttotally depleted from graphene walls. The distribution of ions of the first and second layers closestto the electrodes in the direction parallel to these are also studied by means of bidimensional densitymaps, showing a clear structural transition from a striped pattern to an hexagonal one with theconcentration of cosolvent and also when the size of the cosolvent molecules increases. Thesetransitions seem to be highly sensitive to the presence of cosolvent molecules in the ionic layersclosest to the electrodes. It was also corroborated that the bidimensional ionic structures persist inthe second ionic layer close to the graphene walls.
This persistence of the bidimensional ionic structure combined with the electric double layer(see refs. [2-5]) strongly conditions the three dimensional ionic structure near charged interfaces inthese dense ionic systems. Moreover, recent studies have shown that this bidimensional structuresappear in ILs in other circumstances, like mixtures with salts, mixtures with other cosolventssolvents like water or when the graphene walls have vacancy defects (see ref. [6]). In this work wereport the formation of these structures when the molecular size of the solvent changes.
Acknowledgments
We acknowledge the supercomputing support from the Galician Supercomputing Centre(CESGA). The financial support of the Spanish Ministry of Economy and Competitiveness throughgrants MAT2014-57943-C3-1-P, MAT2014-57943-C3-2-P and MAT2014- 57943-C3-3-P.Moreover, this work was funded by the Xunta de Galicia (AGRUP2015/11 and GRC ED431C2016/001). All these research projects were partially supported by FEDER. Funding from theEuropean Union (COST Action CM 1206) and by the Galician Network on Ionic Liquids,REGALIs (CN 2014/015) is also acknowledged.
References
[1] B. Docampo-Álvarez, V. Gómez-González, H. Montes-Campos, J. M. Otero-Mato, T. Méndez-Morales, O. Cabeza,& L. M. Varela (2016). J. Phys. Cond. Mat., 28(46), 464001.[2] A. A. Kornyshev, (2007). J. Phys. Chem. B, 111(20), 5545-5557.[3] M. V. Fedorov & A. A. Kornyshev, (2008). J. Phys. Chem. B, 112(38), 11868-11872.[4] M. V. Fedorov, N. Georgi & A. A. Kornyshev, (2010). Electrochem. Commun., 12(2), 296-299.[5] M. Z. Bazant, B. D. Storey & A. A. Kornyshev, (2011). Phys. Rev. Lett., 106(4), 046102(1)-046102(4).[6] H. Montes-Campos, J. M. Otero-Mato, T. Méndez-Morales, O. Cabeza, L. J. Gallego, A. Ciach, R. M. Lynden-Bell& L. M. Varela, (2017). Submitted for publication.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºSimposium Title
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºMolecular Physics at the Edge
Rare gas adsorption on naphthalene: Ab initio intermolecular potentials and
cluster configurations
K. Arteaga Gutiérrez1*, M. Bartolomei1, M. I. Hernández Hernández1, J. Campos Martínez1, J. Hernández Rojas2,
J. Bretón Peña2 1 Instituto de Física Fundamental, CSIC, Serrano 123, 28028, Madrid, España.2 Av. Astrofisico Francisco Sánchez, S/N, 38206 San Cristóbal de La Laguna, Santa Cruz de Tenerife
Introduction
The purpose of this study is to develop potential models capable to accurately describe Ab Initiodata for the interaction between rare gases and Naphthalene (C10H ), whose structure consists of a₈fused pair of benzene rings. In this context two interaction models were used, the atom-atom andatom-bond schemes based on the improved Lennard-Jones representation of the additive pairpotential [1], and three different rare gases (Ar, Ne and He) were considered.
Furthermore, the intermolecular rovibrational states for Naphthalene interacting with Ar, Ne, andHe were calculated employing the DVR (Discrete Variable Representation) [2] scheme, with theparticle-in-a-box wave functions as the basis functions of the system. The FBR (Finite BasisRepresentation) approach with a basis of harmonic oscillator wave functions was used too. Theobtained results were compared with those available in the bibliography [3].
Finally, a global optimization technique, the Basin-Hopping algorithm [4] was employed to find theminimum energy structure of Naphthalene--rare gas clusters of increasing size, and C10H -Ar₈ (N)
with N from 1 to 36; and C10H -Ne₈ (N) with N from 1 to 46 and C10H -He₈ (N) with N from 1 to 70. Ananalysis of the stability of the clusters' structure was also performed, obtaining in this way the firstsolvation layers for the different systems.
Acknowledgments
Acknowledgments to the "Grantía Juvenil" program of CSIC (2ª convocatoria)
References
[1] F. Pirani and S. Brizi, Phys. Chem. Chem. Phys., vol. 10 (2008), p. 5489-5503.[2] D.O. Harris, G.G. Engerholm and W.D. Gwinn, J. Chem. Phys. 43 (1965), p.1515.[3] J. Makarewicz, J Chem Phys., vol. 134 (2011), 10.1063/1.3555765.[4] D. J. Wales and J. P.K. Doye, J. Phys. Chem., vol. 101 (1997), p. 5111-5116.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºMolecular Physics at the Edge
Novel Nano-porous Graphites for Gas Storage and Release
M. Bartolomei1*, G. Giorgi2
1 Instituto de Fisica Fundamental – CSIC, Madrid, España2 Dipartimento di Ingegneria Civile ed Ambientale (DICA), Università di Perugia, Italia
Pristine graphene is in principle an ideal adsorbing material due to its large specific area, stability,mechanical properties and low weight. Nevertheless, the physisorption of light gas species ongraphene is in general not particularly favourable, being the adsorption energy, mainly determinedby van der Waals interactions, not large enough to guarantee significant storage capacities atstandard temperature and pressure. Intercalation between graphene layers could lead to moreencouraging adsorption energies but, unfortunately, in pure graphite there is no room for any atomicor molecular species to be hosted. A possible solution to this problem is the use of porous derivativeof graphene as “building blocks” to construct a new class of porous graphites characterized by alarger interlayer volume available for gas storage. To this regard graphynes, which are novel twodimensional (2D) carbonbased materials, represent promising candidates since they naturallyexhibit a nanoweblike structure characterized by triangular and regularly distributed subnanometerpores[1]. These intriguing features make them appealing for molecular filtering as shown by recenttheoretical predictions[2]. The possibility to exploit graphynes as ideal media for the reversiblestorage of light gases is here theoretically investigated. The focus is first on molecular hydrogen(H2) and it is found that graphynes are more suited than graphene for gas hosting since they providelarger binding energies at equilibrium distances much closer to the 2D plane. A novel graphitecomposed of graphtriyne stacked sheets is then proposed[3] and its 3D structure is theoreticallyassessed[4] by means of electronic structure and molecular dynamics computations within the DFTlevel of theory. It is found that the novel layered carbon allotrope is almost as compact as pristinegraphite but the inherent porosity of the 2D graphyne sheets and its relative stacking leads tonanochannels that cross the material and whose subnanometer size could allow the diffusion andstorage of gas species. A molecular prototype of the nanochannel is used to accurately determine[4]firstprinciples adsorption energies and enthalpies for CO2, N2, H2O, and H2 within the pores. Theproposed porous graphite presents no relevant barrier for gas diffusion and shows a significantpreferential physisorption of CO2 with respect to the other relevant components in both pre andpostcombustion gas streams.
References
[1] G. Li et al., Chem. Commun. 46 (2010) 32563258.[2] M. Bartolomei et al., J. Phys. Chem. Lett. 5 (2014) 751755; J. Phys. Chem. C 118 (2014) 2996629972.[3] M. Bartolomei et al., Carbon 95 (2015) 10761081.[4] M. Bartolomei, G. Giorgi, ACS Appl. Mater. Interfaces 8 (2016) 27996−28003.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºSimposium Title
Quantum-Mechanical Simulations of the Transport of Atoms through
Nanoporous Membranes
J. Campos-Martínez1,*, A. Gijón1, M. I. Hernández1 1 Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (IFF-CSIC), C/ Serrano 123, 28006 Madrid, Spain
Introduction
Two-dimensional (2D) membranes composed by (sub-)nanometer pores are allowing gasseparation applications at the molecular level[1]. Confinement provided by these pores can enhancequantum effects in the dynamics of light atoms and molecules, such as zero point energy (ZPE) andtunneling. As these effects are mass-dependent, they might be used for isotopic separation (quantumsieving). There is a large literature where these processes are studied by means of classicaldynamics with quantum corrections or approximate quantum models. We believe that accuratequantum-mechanical calculations are crucial to assess the reliability of the more approximatemethods. For instance, ZPE and tunneling work in opposite directions: while tunneling increases thetransmission rate of a given species, ZPE causes the opposite effect since it involves a higher“effective” potential barrier. Thus, accurate calculations are needed to account for the delicatebalance between the above mentioned quantum features and to search for another quantum effectsthat might play a role in the overall process.
In this contribution we present simulations for the transmission of an atom through a rigidperiodic 2D membrane using a recently reported three-dimensional wave packet (WP3D)propagation treatment[2]. Transmission probabilities and rate coefficients are presented for thetransport of 3He and 4He through graphdiyne[3] as well as through a holey graphene model[4].Results are compared with tunneling-corrected transition state theory (TST)[5] and the range ofvalidity of this and other (reduced dimensionality) theories is discussed. The appearance of clearevidences of resonance features are also shown.
Calculations and Results
Within the WP3D approach, the time-dependent Schrödinger equation is solved by propagatinga wave packet representing the atom approaching the membrane and, from the calculation of theflux through a surface separating the incident and transmitted wave packet, transmissionprobabilities as functions of the translational energy and rate coefficients as functions of thetemperature are obtained. Details for the theory and calculations can be found in Ref. [2].
For He-graphdiyne, previously reported tunneling-corrected TST estimations are in fairly goodagreement with present calculations, including the behavior with temperature of the selectivity forisotope separation, which is defined as the ratio between the 4He and 3He rate coefficients. Theseresults confirm the previous conclusion that both ZPE and tunneling features are paramount in thissystem but and that neglect of one or another effect in a theoretical model can lead to qualitativelyerroneous results.
For the transport of He isotopes through a leaky graphene model we have found that TST is notreliable as it considerably underestimates the transmission rates at low temperatures. In this systemwe have found that the computed transmission probabilities are highly structured suggesting thepresence of selective adsorption resonances[6]. We will present preliminary results of simulations ofthe decaying of initially prepared adsorbed states[6] in order to understand the role played by theseresonances in the process of transmission through the pores of these 2D materials.
XXXVI Biennial Meeting of the Real Sociedad Española de Física pag nºSimposium Title
Conclusion
We report a three-dimensional wave packet approach to study the transport of atoms throughperiodic one atom-thick membranes which demonstrates the importance of quantum phenomenasuch as tunneling, zero point energy and resonances. This formulation serves to assess the range ofvalidity of more approximate theories. The method can be extended to the study of diatoms or bi-layered membranes, among other more complex systems. Some work along these directions is inprogress.
Acknowledgments
The work is funded by Spanish MINECO grant FIS2013-48275-C2-1-P. A. G. thanks “GarantíaJuvenil” C.S.I.C. program. Allocation of computing time by CESGA is also acknowledged.
References
[1] S. P. Koenig, L. Wang, J. Pellegrino, J. S. Bunch, Nat. Nanotechnol. 7 (2012) 728.[2] A. Gijón, J. Campos-Martínez, M. I. Hernández, submitted to J. Phys. Chem. C. (2017).[3] M. Bartolomei, E. Carmona-Novillo, M. I. Hernández, J. Campos-Martínez, F. Pirani, G. Giorgi, J. Phys. Chem. C118 (2014) 29966.[4] C. Sun, M. S. H. Boutilier, H. Au, P. Poesio, B. Bai, R. Karnik, N. G. Hadjiconstantinou, Langmuir 30 (2014) 675.[5] M. I. Hernández, M. Bartolomei, J. Campos-Martínez, J. Phys. Chem. A 119 (2015) 10743.[6] M. I. Hernández, J. Campos-Martínez, S. Miret-Artés, R. D. Coalson, Phys. Rev. B 49 (1994) 8300.
XXXVI Reunión Bienal de la Real Sociedad Española de FísicaMolecular physics at the edge
Noncovalent interactions between cisplatin and graphene prototypes
M. R. Cuevas-Flores1,2*, M. Bartolomei2, M.A. García-Revilla1.
1 Universidad de Guanajuato. Noria Alta s/n, 32050, Guanajuato, México.2 Instituto de Física Fundamental. Consejo Superior de Investigaciones Científicas, C/ Serrano, 123 28006,Madrid, España.
Cisplatin (CP) belongs to the most widely used anticancer drugs and it has been employed formore than 30 years despite the related severe side effects due to its low bioavailability and poorspecificity. For this reason the study and design of novel nanomaterials capable to effectively deliverthe CP drug to the biological target is paramount and still represent a great challenge[1]. The CP planar-square geometry, together with its low water solubility, suggests that it could have a propensity for thephysical adsorption on 2D graphene (G) nanostructures through the interaction with the related highlyconjuated -electron system. As a matter of fact, it has been recently shown that G is capable toefficiently adsorb biological substances of different kinds such as anti-cancer drugs, antibodies,peptides, DNA, RNA, genes[2-5], through noncovalent interactions.
In the present contribution pyrene (P) was selected as the minimum approximation to the G planewhich allow to properly study the noncovalent interactions determining the CP physical adsorption. Inparticular, electronic structure calculations at the Coupled Second-order Moller-Plesset PerturbationTheory (MP2C) [6] level, together with large basis set, allowed to obtain benchmark interaction energyprofiles for several limiting configurations of the CP-P complex. Moreover, in order to assess the roleof the different contributions to the total interaction energy, Density Functional Theory-SymmetryAdapted (DFT-SAPT)[7] computations were performed for specific and particularly attractiveconfigurations of the CP-P complex: we found that the parallel configurations of the aggregate aremainly stabilized around the minimum region by the dispersion energy contribution, in a similar way asin complexes bonded through - interactions.
The reference MP2C interaction energies were also used to test the corresponding estimationsobtained with different functionals within the DFT level, which necessarily includes empiricaldispersion corrections[8], and which is more computationally affordable and practically unavoidable tostudy the interaction of CP with G prototypes of size significantly larger than that of P. An optimaldensity functional was validated and then safely applied to obtain the interaction energy of CP adsorbedon different prototypes of increasing size, ranging from coronene (C24H12) and ovalene (C32H14) toC150H30.
DFT geometry optimizations and frequency calculations, together with an ad hoc extrapolation,allowed a reliable estimation of the adsorption enthapy of CP on G at 298K and 1 bar: we obtained a
particularly favourable value (about -20 kcal-mol-1) being practically double that (about -10 kcal-
mol-1) estimated for the corresponding benzene adsorption, which is in good agreement with recentexperimental findings[9].
Acknowledgments
XXXVI Reunión Bienal de la Real Sociedad Española de FísicaMolecular physics at the edge
We acknowledge the i-COOP+ program of CSIC, the Consejo Nacional de Ciencia y Tecnología(CONACYT, México), the Universidad de Guanajuato and the Universidad Autónoma de ZacatecasMéxico for the support to this research work.
References
[1] T. C. Johnstone, K. Suntharalingam, S. J. Lippard, Chem. Rev. 116 (2016) 3436−3486.[2] V. Georgakilas, M. Otyepka, A. B. Bourlinos, et al., Chem. Rev. 6 (2012) 6156-6214.[3] J. Liu, L. Cui, D. Losic, Acta Biomaterialia 9 (2013) 9243-9257.[4] C. McCallion, J. Burthem, K. Rees-Unwin, A. Golovanov, A. Pluen, Europeam Jornal of Pharmaceutics andBiopharmaceutics 104 (2016) 235-250.[5] S. Syama, P.V. Mohanan, International Jornal of Biological Macromolecules 86 (2016) 546-555.[6] M. Pitonak and A. Hesselman, J.Chem. Theory Comput. 6 (2010) 168-178.[7] A. Hesselman, G. Jensen and M. Schutz, J. Chem. Phys. 122 (2005) 014103.[8] S. Grimme, S. Ehrlich, and L. Goerigk, J. Comput. Chem. 32 (2011) 1456.[9] E. Otyepkova, P. Lazar, K. Cepe et al., Applied Materials Today 5 (2016) 142-149.
XXXVI Reunión Bienal de la Real Sociedad Española de FísicaTítulo Simposio
Molecular Dynamics Study of Mixtures of Protic and Aprotic ILs and the Effects
of Alkyl Chain Length
B. Docampo-Álvarez 1, V. Gómez-González1, J.R. Rodríguez1, L.J. Gallego1, O. Cabeza2, L.M. Varela1,*
1 Grupo de Nanomateriais, Fotónica e Materia Branda, Departamentos de Física de Partículas e de Física Aplicada, Universidade de Santiago de Compostela, Campus Vida s/n E-15782, Santiago de Compostela, Spain2Departamento de Física y Ciencias de la Tierra, Facultade de Ciencias, Universidade da Coruña, Campus A Zapateira s/n, E-15071 ACoruña, Spain
Introduction
Ionic liquids (ILs) have been the focus of much research in recent times due to the largenumber of possible applications these 'designer solvents' have. Mixing two or more ILs furtherenhances their tunable nature; however, most of the research in the subject has focused on mixturesof similar ILs from the same family (Ref. [1]). Here we report the results of our studies of protic-aprotic IL mixtures of the protic ILs ethylammonium nitrate (EAN) and butylammonium nitrate(BAN) with the aprotic ILs 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF4] and 1-buthyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4], by means of Molecular Dynamics(MD) simulations, as well as experimental density and conductivity measurements.
The marked differences between both ionic liquid families result in a rich behavior in theelectric conductivity curve of the mixtures, most markedly in the EAN-[EMIM][BF4] mixture (Ref.[2]). This is shown to arise from the interplay of the different self-structuring forces of the liquid,with the hydrogen bonding interactions of the protic component becoming dominant at very lowconcentrations. At these concentrations, changes in both the conductivity curve (with a globalminimum and, in some cases, a local maximum), and in magnitudes such as radial and spatialdistribution functions and diffusion coefficients can be observed.
A study of the influence of the length of the alkyl chain present in cations further reveals theirimportance in the nanostructure of the mixture. Longer chains, which are known to lead to theformation of polar and apolar domains (ref. [3]), subtly alter the structure of the liquid, with shorterchain cations showing a preference for positions near the longer alkyl chain. An attempt is made torelate this to the subtle shifts in macroscopic properties observed between families.
Acknowledgements
The financial support of the Spanish Ministry of Economy and Competitiveness (Project Nos.MAT2014-57943-C3-1-P, MAT2014-57943-C3-2-P, MAT2014-57943-C3-3-P, and FIS2012-33126)is gratefully acknowledged. Moreover, this work was funded by the Xunta de Galicia (Project Nos.AGRUP2015/11 and GRC ED431C 2016/001). All these research projects were partially supportedby FEDER.V. Gómez-González thanks the Spanish ministry of Education for his FPU grant.Facilities provided by the Galician Supercomputing Centre (CESGA) are also acknowledged.
References
[1] H. Niedermeyer, J.P. Hallett, I.J. Villar-Garcia, P.A. Hunt, T. Welton, Chem. Soc. Rev. 41 (2012) 7780-7802[2] B. Docampo-Álvarez, V. Gómez-González, T. Méndez-Morales, J. R. Rodríguez, E. López-Lago, O. Cabeza, L. J.Gallego, L. M. Varela, Phys. Chem. Chem. Phys. 18(34) (2016) 23932-23943[3] J.N.A. Canongia Lopes, A.A.H. Padua, J. Phys. Chem. B 110 (7) (2006) 3330–3335