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O: Fachverband Oberflächenphysik

O 63: Focus Session: Functional Molecules at Surfaces III

O 63.8: Vortrag

Mittwoch, 18. März 2020, 12:30–12:45, TRE Ma

Weakly-bound supramolecular structures: calculations for understanding experiments with the scanning tunneling microscope — •Roberto Robles¹, Vladimír Zobač¹, Kwan Ho Au Yeung², Francesca Moresco², Dmitry Ryndyk², Christian Joachim³, and Nicolás Lorente^1,4 — ¹Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), San Sebastián, Spain — ²Center for Advancing Electronics Dresden, TU Dresden, Germany — ³Centre d’Elaboration de Matériaux et d’Études Structurales (CEMES), CNRS, Université de Toulouse, Toulouse, France — ⁴Donostia International Physics Center (DIPC), San Sebastián, Spain

4-Acetylbiphenyl is a small aromatic molecule that binds via dispersive forces (van der Waals) with a gold surface. Experiments performed in the group of Dr. Moresco in TU Dresden showed that, under certain conditions of deposition, these molecules formed a 4-molecule superstructure nicknamed the "windmill" because of its cross-shaped structure. These "windmills" are reproducible, directional and resilient to external interactions. Closer inspection of the scanning tunneling microscope images (STM) reveals that the unique seemingly H-bond should take place between a methyl group and the O atoms. This is one of the weakest H bonds if it binds at all. We undertook density functional theory calculations completed by empirical van-der-Waals corrections to study the supramolecular structure. From the simulation of STM images, total energy calculations and Gibbs free-energy estimates, we reach the conclusion that windmills are likely to involve gold adatoms to join the four acetylbiphenyl molecules together.