Surface-sandwich segregation on nondilute bimetallic alloys: Pt50Ni50 and Pt78Ni22 probed by low-energy electron diffraction.

Abstract

A short-wave large-amplitude compositional oscillation versus depth at the (111) surface of ${\mathrm{Pt}}_{50}$${\mathrm{Ni}}_{50}$ and ${\mathrm{Pt}}_{78}$${\mathrm{Ni}}_{22}$ alloys is observed by means of low-energy electron diffraction (LEED). In the LEED calculation, the substitutional disorder of the alloys is successfully mimicked by the averaged t-matrix approximation. The occurrence of a well-developed Pt-Ni surface sandwich on top of the Pt-Ni alloys is interesting in view of the chemisorptive and catalytic properties of these alloys.