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Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 62: Metal Substrates: Adsorption of Inorganic Molecules

O 62.9: Talk

Thursday, February 28, 2008, 11:30–11:45, MA 042

Monte-Carlo lattice gas simulation of the thermal desorption behavior of CO from PtxAu1−x/Pt(111) surface alloys — •Harry E. Hoster1, Yoshihiro Gohda2, Andreas Bergbreiter1, Menhild Eyrich1, Joachim Bansmann1, Axel Groß2, and R. Jürgen Behm11Institute of Surface Chemistry and Catalysis, Ulm University, 89069 Ulm, Germany — 2Institute of Theoretical Chemistry, Ulm University, 89069 Ulm, Germany

The thermal desorption behavior of CO adsorbed on PtxAu1−x/Pt(111) surface alloys was studied by Monte Carlo simulations in a lattice gas approximation [1,2], comparing different Pt:Au ratios and initial COad coverages. Based on thermal desorption data and DFT calculations, the CO molecules preferentially occupy Pt on-top sites of PtxAu1−x/Pt(111) surface alloys, and the adsorption energies are approximately constant for different numbers of neighboring Au atoms (ligands). Au sites are not occupied at room temperature. The atomic distribution in the surface layer used in the simulations was derived from STM data with chemical contrast, and the adsorption energies stem from DFT calculations. At higher COad-coverages, the CO-CO repulsions are considered via a pair interaction parameter determined by fitting to the experimental data. The accuracy of the lattice gas approach for inhomogeneous surfaces is discussed by comparing with the experimental thermal desorption data.

[1] J.L.Sales, G.Zgrablich, V.P.Zhdanov, Surf.Sci 209(1989)208

[2] V.P.Zhdanov, J.L.Sales, R.O.Unac, Surf.Sci.Lett.381(1997)L599

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