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O: Fachverband Oberflächenphysik

O 35: Poster Session I (Metal, semiconductor and oxide substrates: structure and adsorbates; Graphene)

O 35.40: Poster

Dienstag, 12. März 2013, 18:15–21:45, Poster B1

Adsorbate-induced segregation: a quantitative first-principles study for C/Pt₂₅Rh₇₅(100) — •Tobias C. Kerscher¹, Wolfgang Landgraf², David Reith³, Raimund Podloucky³, and Stefan Müller¹ — ¹TU Hamburg-Harburg — ²Universität Erlangen-Nürnberg — ³Universität Wien

For catalytic surfaces, such as Pt-Rh, it is essential to understand the change in the segregation profile due to the presence of adsorbates. Our prior first-principles studies of adsorbate-induced segregation in C/Pt₂₅Rh₇₅(100) have shown that, compared to the clean surface, a small amount of carbon impurities suffices to substantially decrease the Pt concentration in the top layer of the substrate. We corroborated this view at T=0 K by DFT and the cluster expansion (CE).

Now, we have improved the CE to increase its accuracy for the complex interactions between several substrate and adsorbate layers. This enables us to quantitatively predict the T-dependent, layer-by-layer segregation profile of the substrate subject to C-contamination [1]. Our CE code UNCLE [2] uses a bisection of the simulation lattice into separate subsystems—already discussed during the last years—in combination with a new averaging procedure [3]. We discuss the coupling of the substrate and adsorbate layers in the CE, the T=0 K stability diagram, and the T-dependent segregation profile for different C-contaminations. (Supported by DFG.)
[1] T. C. Kerscher et al., Phys. Rev. B 86, 195420 (2012)
[2] D. Lerch et al., Modelling Simul. Mater. Sci. Eng. 17 (2009), 055003
[3] D. Reith et al., Phys. Rev. B 86, 020201(R) (2012)