ON THE CONSPICUOUS SEGREGATION BEHAVIOR AT Pt–Rh SURFACES

Phase demixing is evaluated as a possible explanation for the anomalous temperature dependence of the Pt segregation at the Pt50Rh50(511), Pt25Rh75(110) and Pt25Rh75(100) surfaces. Calculations are performed in the quasichemical approximation and a broken bond scheme. Although the calculations based on systematic demixing tend to overestimate the surface enrichment, the qualitative agreement appears to be rather good.