Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 36: Structure and dynamics

O 36.4: Talk

Thursday, March 30, 2006, 12:00–12:15, WIL C207

First-principles based ground-state analysis of Co subsurface segregation in CoAl(111) — •Christian Riedl, Ole Wieckhorst, Stefan Müller, Lutz Hammer, and Klaus Heinz — Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen

As recently shown [1,2], the segregation profile of B2-ordered CoAl surfaces is controlled by tiny off-stoichiometries (Co antisite atoms). By applying the combination of density functional theory with the cluster expansion method and genetic algorithms we present the surface stability diagram of CoAl(111) considering the energetics of thousands of geometrically fully relaxed surface structures. It turns out that Al-Co-Co-Co layer stacking is clearly the most stable configuration in agreement with our earlier DFT and quantitative LEED analysis [2]. We discuss the electronic structure providing reasons for the stability of the Al-Co-Co-Co layer stacking. Furthermore, subsequent Monte-Carlo-simulations allow for the determination of the temperature dependent segregation profile up to the 7th layer as well as for an analysis of substitutional ordering at the surface.

[1] V. Blum et al, Phys. Rev. Lett. 89, 266102 (2002)

[2] L. Hammer et al., Phys. Rev. B 71, 075413 (2005)