Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 41: Inorganic/Organic Interfaces

O 41.17: Poster

Dienstag, 17. März 2015, 18:15–21:00, Poster B

Ab initio thermodynamical study of thiolate adsorption on Au(111) using the vdW-DF-CX functional — •Joakim Löfgren, Henrik Grönbeck, Kasper Moth-Poulsen, and Paul Erhart — Chalmers University Of Technology, Gothenburg, Sweden

Adsorption of alkylthiolates on Au(111) and the formation of self-assembled monolayers (SAMs) has been extensively studied for several decades and is important for many applications in e.g., sensing and nanofabrication. In the years, understanding of the interface and adsorption geometry has been elucidated by the combined efforts of experiment and density functional theory (DFT) calculations. One of the key challenges for DFT calculations of SAMs is the description of van-der-Waals type interactions, which are not captured in conventional exchange-correlation (XC) functionals. As a result, DFT studies have struggled to describe alkylthiolate SAMs with longer hydrocarbon chains. Here, we present DFT calculations based on the recently developed vdW-DF-CX functional, which properly accounts for dispersive interactions while providing an excellent description of both the late transition metals and covalently-bonded systems. We investigate several adsorption geometries suggested in the literature and show that the CX functional gives results that are consistent with experimental findings for short alkyl chains while, in contrast to e.g., generalized-gradient XC functionals, also yields excellent results for chain-chain and chain-substrate interactions for longer alkyl chains. We further examine the relative stability of striped and standing-up phases at different coverages as a function of the chemical environment.