Regensburg 2013 – scientific programme
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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
Tuesday, March 12, 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)