Electronic structure and character of long-period superstructures in precious-metal alloys

Abstract

Based on ab initio calculations of the electronic structure, an attempt is made to identify reasons for the qualitatively different character of long-period superstructures (LPS) with large and small superperiods 2 M in alloys of noble metals. Two different groups of alloys were investigated: Au 3Cu and Cu 3Pd (of relatively large M) and Ag 3Mg (of relatively small M). The nature of two-dimensional incommensurate LPS in the Au 3 Cu and Cu 3 Pd has been revealed. Analysis of the relationship between the nesting properties of the Fermi surface (FS) and the structure of LPS in the alloys under study is performed. It is shown that the dependence of LPS character on the value of 2 M is controlled by the quality of nesting on the Fermi surface and sensitivity of the nesting vector 2 k → F to variations in the long-range order parameter.