Regensburg 2004 – scientific programme

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O: Oberflächenphysik

O 43: Adsorption an Oberflächen IV

O 43.7: Talk

Friday, March 12, 2004, 12:45–13:00, H36

Semi-Empirical Potentials for Studying Catalytic Processes ? — •Bernhard Lehner, Karsten Reuter, and Matthias Scheffler — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin

Ab initio electronic structure calculations like density functional theory (DFT) significantly contribute to the understanding of catalytic processes at solid surfaces, but are currently limited to microscopic system sizes and time scales. A promising approach to reach mesoscopic and macroscopic regimes is to use semi-empiric potentials, parameterised from ab initio calculations. The main challenges in the development of such an intermediate potential are high accuracy and reliability.

We check the suitability of Modified Embedded Atom Method (MEAM) potentials for interpolating (and the possibility of extrapolating) DFT data for a description of oxidation reactions on metal surfaces (Al, Pd, ..). Possible extentions of the MEAM promising higher accuracy and flexibility are also discussed. The potential-energy surfaces of atomic oxygen adsorbed at low index facets, calculated by DFT, are used to determine the free parameters of the semi-empiric potential. The MEAM is found to be perfectly suitable for interpolating between the DFT data points. The extrapolation capabilities of the semi-empiric potential are discussed by examining the adsorption and desorption features predicted for surfaces not included in the construction of the potential. In particular, the capability of MEAM to reproduce the preferred adsorption of oxygen at step edges of vicinal surfaces is discussed.