Effective-medium calculations for an amorphous metallic alloy.

Abstract

The reliability of effective-medium theories (EMT's) for describing the electronic structure of amorphous metallic alloys is tested for the particular example of amorphous ${\mathrm{Zr}}_{70}$${\mathrm{Cu}}_{30}$, modeled by a tight-binding Hamiltonian. Two different approximations are investigated: the Ishida-Yonezawa theory, which renormalizes locators only, and a simplified version of Roth's effective-medium approximation, which renormalizes both locators and interactors. The calculated electronic densities of states (DOS's) are compared with our previous results obtained by the recursion method based on an amorphous cluster generated by molecular dynamics. The use of different model partial radial distribution functions as input for the effective-medium calculations is investigated. Although the recursion-method DOS is roughly reproduced, the different EMT's yield dissimilar results. We conclude that the simple EMT's studied in this work may be useful for amorphous metallic alloys when studying the effect of the short-range order on the electronic DOS.