Regensburg 2013 – scientific programme

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O: Fachverband Oberflächenphysik

O 52: Organic/bio Molecules on Metal Surfaces V

O 52.11: Talk

Wednesday, March 13, 2013, 18:30–18:45, H38

The role of dispersion forces in SAM(aromatic thiolates)/Au(111) systems: a DFT study including semi-empirical dispersion corrections — •Jan Kučera and Axel Groß — Institut für Theoretische Chemie, Universität Ulm, D-89069 Ulm, Germany

The anchoring of aromatic thiolates on metal substrates has been widely used as a feasible method to effectively modify the electronic properties of environment/metal interfaces intended as, e.g., components of new nanoelectronic devices. The theoretical description of those systems represents a rather complex task since also noncovalent effects as, e.g., van der Waals (vdW) interactions operate in the formation of the complexes.

We performed periodic density functional theory (DFT) calculations with semiempirical DFT-D3 [1] and DFT+vdW [2] corrections to clarify the role of dispersion in the molecule-surface as well as in the molecule-molecule interaction. To be specific, we addressed SAM/Au(111) complexes with the SAM formed by di-4-pyridine-di-sulphide (PySSPy), 4-mercaptopyridine (SPy), and 4-(4-mercaptophenyl) pyridine (SPhPy) molecules. We find that the stability of the PySSPy/Au complex is dominated by dispersion. In contrast, covalent bonding is the structure- and stability-determining factor in SPy and SPhPy/Au complexes, where dispersion only significantly contributes to the molecule-substrate interaction.

[1] S. Grimme et al., J. Chem. Phys. 132, 154104 (2010).

[2] A. Tkatchenko and M. Scheffler, PRL 102, 073005 (2009).