Dresden 2009 – scientific programme
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O: Fachverband Oberflächenphysik
O 18: Metal substrates: Adsorption of organic / bio molecules III
O 18.8: Talk
Tuesday, March 24, 2009, 12:15–12:30, SCH A118
First-principles and semi-empirical van der Waals studies of pyridine and thymine on the Cu(110) surface — •V. Caciuc1, N. Atodiresei1, P. Lazić1, J.-H. Franke2, Y. Morikawa3, and S. Blügel1 — 1Institut für Festkörperforschung, Theorie I, Forschungszentrum Jülich, D-52425 Jülich, Germany — 2Physikalisches Institut, Westfälische Wilhelms Universität Münster, Wilhelm-Klemm-Str. 10, D-48149 Münster, Germany — 3The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki Osaka, 567-0047 Japan
We performed density functional calculations aimed to investigate the adsorption geometry and bonding mechanism of a single pyridine (C5H5N) and thymine (C5H6N2O2) molecule on the Cu(110) surface. In the ground state, the pyridine molecule adsorbs with its molecular plane perpendicular to the substrate and is oriented along the [001]-direction while the thymine is aligned along the [110]-direction. For this adsorption configuration, the bonding mechanism of these molecules involves a strong hybridization between the highest occupied molecular orbitals (HOMOs) and the d-states of the substrate. However, when the molecular plane is parallel to surface, the long-range van der Waals interactions play an important role on both the molecule-surface geometry and the adsorption energy. Their specific role was analyzed by means of a semi-empirical and the seamless methods. In particular, for a planar configuration, the inclusion of the dispersion effects can dramatically change the character of the adsorption process from physisorption to chemisorption.