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Reliable computational prediction of the supramolecular ordering of complex molecules under electrochemical conditions

: Hartl, B.; Sharma, S.; Brügner, O.; Mertens, S.F.L.; Walter, M.; Kahl, G.

Fulltext ()

Journal of chemical theory and computation : JCTC 18 (2020), No.6, pp.5227-5243
ISSN: 1549-9618
ISSN: 1549-9626
Deutsche Forschungsgemeinschaft DFG
WA 1687/10-1; HYBRIDIS
Journal Article, Electronic Publication
Fraunhofer IWM ()
Silver-111; Liquid-solid Interfaces; Scanning Tunnelling Microscopy

We propose a computationally lean, two-stage approach that reliably predicts self-assembly behavior of complex charged molecules on metallic surfaces under electrochemical conditions. Stage one uses ab initio simulations to provide reference data for the energies (evaluated for archetypical configurations) to fit the parameters of a conceptually much simpler and computationally less expensive force field of the molecules: classical, spherical particles, representing the respective atomic entities; a flat and perfectly conducting wall represents the metallic surface. Stage two feeds the energies that emerge from this force field into highly efficient and reliable optimization techniques to identify via energy minimization the ordered ground-state configurations of the molecules. We demonstr ate the power of our approach by successfully reproducing, on a semiquantitative level, the intricate supramolecular ordering observed experimentally for PQP+ and ClO4- molecules at an Au(111)-electrolyte interface, including the formation of open-porous, self-host-guest, and stratified bilayer phases as a function of the electric field at the solid-liquid interface. We also discuss the role of the perchlorate ions in the self-assembly process, whose positions could not be identified in the related experimental investigations.