Dresden 2009 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
O: Fachverband Oberflächenphysik
O 56: Metal substrates: Epitaxy, growth and adsorbates
O 56.13: Vortrag
Donnerstag, 26. März 2009, 18:00–18:15, SCH A316
Influence of C-adsorption on the segregation profile of Pt25Rh75(100)
— •Wolfgang Landgraf, Tobias Kerscher, and Stefan Müller — Universität Erlangen-Nürnberg, Lehrstuhl für Theoretische Physik 2, Staudtstr. 7, D-91058 Erlangen
As found earlier by experiment [1] and theory [2], the (100) and (111) surfaces
of the alloy system Pt25Rh75 show a strong Pt enrichment
in the top atomic layer and a Pt depletion in the layer underneath.
However, from experiment [1], it appears that for the (100) orientation
even a small amount of carbon impurity leads to a considerable decrease
in the Pt top layer concentration.
We applied density functional theory to analyze quantitatively the influence
of C-adsorption on the segregation profile of Pt25Rh75(100).
Indeed, we find that the segregation profile tremendously change as function
of the C-coverage: Already at Θ = 0.5 the configuration being
lowest in energy consists of carbon atoms in hollow sites and
pure Rh-layers in the near surface regime. The correlations between structural
and energetic properties will be discussed. The corresponding energetics
can be used for the construction of a cluster expansion Hamiltonian in order to predict
the alloy’s most stable segregation profile for
arbitrary carbon coverage.
Supported by Deutsche Forschungs-Gemeinschaft
[1] E. Platzgummer et al., Surf. Sci. 419, 236 (1999).
[2] S. Müller, M. Stöhr, O. Wieckhorst, Appl. Phys. A. 82, 415 (2006).