Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 49: Surface chemical reactions I
O 49.6: Vortrag
Mittwoch, 24. März 2010, 11:45–12:00, H42
’QM/Me’ - a novel embedding approach for adsorbate dynamics on metal surfaces — •Jörg Meyer1 and Karsten Reuter1,2 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany) — 2Technische Universität München (Germany)
The dissociative adsorption of oxygen molecules on metal surfaces is a commonly known, highly exothermic reaction and in its slow or fast form of great importance for corrosion or oxidation catalysis, respectively. However, knowledge about atomistic details of the heat dissipation, a central conceptual concern, is very limited at best. Even on the level of Born-Oppenheimer potential energy surfaces, accurate dynamical ab-initio descriptions of such reactions are quite challenging from a computational point of view: Modeling the excitations of substrate phonons within periodic boundary conditions requires huge supercells, whereas traditional ’QM/MM’ embedding schemes do demand unfeasibly large metal clusters. In the novel ’QM/Me’ approach presented here, the adsorbate-substrate interaction is obtained from periodic first-principles calculations in convenient supercells and combined with the description of a ’bath-like’ substrate based on classical potentials, which are parametrized to seamlessly fit the first-principles data. We apply our approach to dissociative adsorption of O2 and H2 on Pd(100) using density-functional theory and a modified embedded atom potential. In both cases, we observe a dominant fraction of the released chemisorption energy to be dissipated into the bulk already on a femtosecond time scale. Implications for the adsorbate dynamics will be discussed.