Berlin 2008 – scientific programme
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O: Fachverband Oberflächenphysik
O 74: Metal Substrates: Adsorption of O and/or H
O 74.4: Talk
Thursday, February 28, 2008, 15:45–16:00, MA 141
Hot adatom motion tackled from first-principles — •Jörg Meyer and Karsten Reuter — Fritz-Haber-Institut, Faradayweg 4-6, D-14195 Berlin (Germany)
The initial stages of the oxidation of metal surfaces are still far from being understood - despite their essential importance for example in the field of oxidation catalysis. In view of the exothermicity of the dissociative adsorption of O2 at most metal surfaces, one fundamental question concerns the energy dissipation into the substrate, which, if sufficiently slow, could give rise to a transient mobility of the adsorbed, but not yet equilibrated oxygen atoms. In order to address this issue by first-principles theory we separate the molecular encounter with the surface into two stages: At large distances from the surface, substrate mobility can still be neglected and we focus our density-functional theory calculations on the six-dimensional potential-energy surface (PES) representing the molecular degrees of freedom. Performing extensive molecular dynamics (MD) runs on this suitably interpolated PES we evaluate the steering of thermal molecules into specific entrance channels. The corresponding molecular orientations and positions at intermediate heights above the surface form then statistically relevant starting geometries for first-principles MD trajectories of the remaining dissociation path that consider a full substrate mobility in large surface unit-cells. Applying this scheme to the O2 dissociation over Pd(100), we will critically discuss a possible transient mobility especially in view of the restrictions on phononic dissipation inside the employed supercell geometry.