cp2k workshop seminar 2901142014_user... · andrea floris king’s college london • create chiral...
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Surface Science Reaserch Center University of Liverpool Rasmita Raval Sam Haq Bart Wit
King’s College London Lev Kantorovich
Sang Hongqian
Covalent self-assembly: steering highly directional nanostructures of
porphyrins on Cu(110)
Andrea Floris King’s College London
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• create chiral structures
• create particularly large domains on the surface
• create a networks with nanopores N. Abdurakhmanova, A. Floris et al., Nature Comm. (2012) • • change the surface work function • study the formation of highly selective structures
Functionalizing a surface by molecular self-assembly
A. Floris, A. Comisso, A. De Vita, ACS Nano (2013)
- + -
G. Tomba et al, ACS Nano (2010)
M.-C. Blüm et al., Angew. Chem. (2005)
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• Surface-molecule (SM) and molecule-molecule (MM) interactions made of covalent bonds
(strong w.r.t. vdW, H-bond or electrostatic interactions)
• Very robust structures
Covalent self-assembly
Self-assembled functionalized porphyrins on Cu(110)
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Molecule: Tri-Methyl-Tetra-Phenyl-Porphyrin (TMTPP)
phenyls
Pentagons with N: Denoted N
Pentagons with –NH: Pyrroles
core
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Cu(110) surface: rows
001
1-10
[1-10] : “easy” direction (=easy diffusion, along the rows)
[001] : “difficult” direction (=difficult diffusion,perpendicular to the rows)
2.57A
3.64
A
1-10
001
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[001]
[110]
[001]
[110]
[001]
[110]
After annealing (at 550K) : methyl groups connect: chains, zig-zag, 2D structures form
Before annealing (T=300K) : isolated molecules, randomly distributed
Hypothesis: dehydrogenation of peripherical methyls catalyzed by the substrate?
Experimental facts
M. In’t Veld, P. Iavicoli, S.Haq, D. B. Amabilino , R. Raval ,Chem. Comm (2008)
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Goals
1. Find the stable structure on the substrate 2. Understand the bonding mechanism
• geometrical relaxations
• de-hydrogenation
• simulations of STM images, compare with EXP
• diffusion
CP2K : RUN_TYPE= GEO_OPT, with D2-Grimme
• molecular bonding
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Geometry on the substrate
Total energy versus configurations
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Energetics: CP2K versus Quantum-ESRPESSO
CP2K Quantum-ESPRESSO
Very good agreement
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Geometries on the substrate
Two most stable configurations
Conf 11: Most stable (0 eV): • Horizontal pyrroles • vertical N • slightly rotated phenyls • 2 N-Cu bond • 4 C-Cu bonds • Horizontal phenyls exposed to the substrate (vdW) • 6 bonds
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Conf 9, rotated 90 deg (+0.518 eV): • Similar to conf11 • NO C-Cu bonds
Geometries on the substrate
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De-hydrogenation: H removal at T=0K
• Removing a H at T=0K H costs energy • Peripherical H: the easiest to remove iii(~0.35eV)
• Core central H also “easy”
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Relax upon peripherical H removal
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H de-adsorption: role of T crucial
Experimentally at T=300K: • No bonding is observed
• No H de-adsorption is observed
H de-adsorption starts at 500K
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Molecular diffusion: Nudge Elastic Bands (NEB)
• Diffusion is much more favourable along the rows
• DH does not affect diffusion along rows, while it does across
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Molecular bonding: energy barriers
3 consecutive processes: • 1st dehydrogenation • 2nd dehydrogenation • diffusion-bonding
CP2K RUN_TYPE=BAND
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V=-0.284 I=0.26nA
CONF11 (stable) V=-0.5 I=1.E-07
CONF9 (+0.518eV) V=-0.284 I=1.E-06
STM: theory versus experiment
CONF15 (+1.09eV) V=-0.5 I=0.6E-07
• Quantum-ESPRESSO (ILDOS) • LEV00 (simulation of STM at constant current) iiiihttp://www.cmmp.ucl.ac.uk/~lev/codes/lev00/
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TMTPP chains CoDPP chains
• Steering different directions via different functional groups
1D structures
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Walker molecule
Ph.D students: Bart Wit Sang Hongqian
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Diffusion lines observed by STM
B. Wit, S. Hongqian, S. Haq, A. Floris, L. Kantorovich, D. Amabilino, R. Raval, to be published
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“Walking” mechanism along the rows
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“Walking” mechanism along the rows
B. Wit, S. Hongqian, S. Haq, A. Floris, L. Kantorovich, D. Amabilino, R. Raval, to be published
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Summary
1) Surface functionalization via self-assembled molecules 2) Functionalized porphyrins realize robust, covalent structures by heating 3) Bonding mechanism: dehydrogenation, diffusion, bonding
4) 1D fences and walking molecules: huge playground for creating specific patterns iiiion substrates 5) CP2K: • Very good agreement with PW codes. • Efficient RUN_TYPE= GEO_OPT and BAND