On the electronic structure of surface Pt-Sn alloys

The electronic structures of Pt3Sn(111),Pt3Sn/Pt(111) and Pt2Sn/Pt(111) sur faces are studied using the linear-muffin-tin-orbital tight-binding method in the atomic-sphere approximation. Both ideal and rumpled surface terminat ions are considered. The hybridization between Pt d- and Sn p-electrons, re spectively, leads to a lowering of the local density of electronic states a t the Fermi level and to a downward shift of the Pt local d-band, which acc ounts for the lower reactivity of the Pt-Sn surfaces. The effect is more pr onounced for rumpled surfaces. Generally, the situation is similar to that of bimetallic transition-metal surfaces. The initial-state approximation is used to predict Pt(4f) con-level shifts. We find moderate shifts of either sign, but the d-band centre of gravity moves to higher binding energies, a s compared to Pt(111), in most cases. The correlation between the surface r eactivity and core-level shifts, respectively, seems to be less favourable than at bimetallic transition-metal surfaces (C) 1999 Elsevier Science B.V. All rights reserved.