On the density of states of disordered alloys and their moments

Abstract

Compares two methods to calculate the density of states n(E) of disordered alloys, both of which use the continued fraction expansion of the Green functions and have the same number of exact moments. In one of the procedures the authors approximate n(E) by the average of local densities of states, each calculated by the continued fraction expansion. In the other, the moments of the alloy are calculated first and from these n(E) is obtained from a single continued fraction. It is shown that, for a tight-binding one-dimensional alloy, the first method is definitely better due to the pronounced structure of the alloy density of states. For more realistic Hamiltonians and for amorphous and liquid systems, both methods may be more comparable.