Problems in Strong-Scattering Binary Alloys

Abstract

We present results of model calculations based on two different approximations which were both intended to be improvements over the coherent potential approximation. We show that both approximations yield nonphysical solutions; specifically, they predict average Green's functions which contain singularities on both the upper and lower halves of the complex energy plane. We conjecture that nonanalytic behavior will occur generally in high-order approximations to the average Green's function.