SIMPLE THEORY OF ELECTRONIC-STRUCTURE CALCULATIONS FOR AMORPHOUS TRANSITION-METAL ALLOYS

A theory of electronic-structure calculations for amorphous alloys is presented on the basis of a geometrical-mean model for amorphous structures and transfer integrals. It greatly simplifies the numerical calculations by constructing the electronic structures of amorphous alloys from those of constituent amorphous pure metals, and describes the local environment effects by introducing the average coordination numbers z(alpha)* and atomic short-range-order parameters tau(alpha) for each type of atom alpha. It is demonstrated, by comparing the numerical results with those obtained from first-principles, that the theory reasonably describes the electronic structure of amorphous transition-metal alloys. In particular, it is shown that the difference in z(alpha)*, which is caused by constituent atoms with different atomic sizes, stabilizes the ferromagnetism in amorphous Fe65Zr35 and Co2Y alloys since it builds up a high-energy peak around the Fermi level.