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O: Fachverband Oberflächenphysik
O 80: Epitaxy and growth: Metals and semiconductors I
O 80.8: Vortrag
Donnerstag, 17. März 2011, 16:45–17:00, WIL C307
Ab-initio study on the temperature dependence of adsorbate-induced segregation in C/Pt25Rh75(100) — •Tobias C. Kerscher and Stefan Müller — Technische Universität Hamburg-Harburg, Institut für Keramische Hochleistungswerkstoffe, Denickestr. 15, 21073 Hamburg, Germany
Understanding the adsorbate-induced segregation of alloy surfaces is essential for catalytic surfaces.
An interesting example is the C/Pt25Rh75(100) system:
In comparison to the clean surface [1,2], even a small amount of carbon impurities leads to a considerable decrease in the Pt concentration of the top layer [1].
Previously, our first principles study of the coupled surface–adsorbate system was restricted to T=0 K, where density functional theory shows that this change in segregation is driven by the antagonism between the segregation energies of Pt and Rh, and their binding energies to C.
Now, we use an ab-initio-based cluster expansion in the framework of the UNCLE code [3] to investigate the T>0 K temperature behaviour of the system by means of Monte Carlo simulations.
We discuss the substitutional ordering of both the carbon adsorbate layer and the four topmost surface layers of Pt25Rh75(100) as a function of temperature and concentration.
Our predictions are compared to experimental data in a quantitative manner.
Supported by Deutsche Forschungsgemeinschaft.
[1] E. Platzgummer et al., Surf. Sci. 419 (1999), 236.
[2] P. Welker et al., J. Phys.: Condens. Matter 22 (2010), 384203.
[3] D. Lerch et al., Model. Simul. Mater. Sci. Eng. 17 (2009), 055003.