Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 36: Structure and dynamics

O 36.6: Talk

Thursday, March 30, 2006, 12:30–12:45, WIL C207

First Principles based prediction of short range order at the Pt₂₅Rh₇₅ (111) surface — •Markus Stöhr, Ole Wieckhorst, and Stefan Müller — Universität Erlangen-Nürnberg, Lehrstuhl für Festkörperphysik, Staudtstr. 7, D-91058 Erlangen, Germany

The disordered Pt₂₅Rh₇₅(111) alloy surface shows a strong tendency towards Pt segregation. Although the segregation profile and atomic position in the near surface layers are well known by earlier STM and LEED studies [1,2], the reasons for the observed behaviour are widely unknown. We have used the combination of density funtional theory (DFT) with cluster expansions and Monte-Carlo-simulations to model the substitutional ordering behaviour of the Pt₂₅Rh₇₅ (111) surface. This approach allows for the determination of the segregation profile, being in good agreement with the experimental data [1,2]. Moreover our approach gives access to the detailed short range order behaviour of the surface, as well as to the geometric structure of the surface.

[1] E. Platzgummer, M. Sporn, R. Koller, S. Forsthuber, M. Schmid, W.Hofer, P. Varga, Surf. Sci. 419 (1999) 236.

[2] E. L. D. Hebenstreit, W. Hebenstreit, M. Schmid, P. Varga, Surf. Sci. 441 (1999) 441.