Application of augmented-space formalism to a problem of configuration averaging in the theory of unordered alloys with correlated disorder

Abstract

We present a method for calculating the electronic spectrum of a binary unordered alloy with short-range order (SRO). The method is based on a generalization of the augmented-space formalism in the case of correlated spatial disorder. A number of schemes for self-consistent calculation of the self-energy of the configurationally averaged Green's function are proposed. This approach guarantees a positive density of states (Herglotz property) for all values of the Cowley SRO parameter \ensuremath{\alpha}. A merit of the method proposed is a correct limiting transition to the Green's function of the ordered alloy when the Cowley SRO parameter tends to the critical value. The approach is in agreement with the known approximations in the case of $\ensuremath{\alpha}=0.$ As an illustration, a numerical analysis of self-consistent equations has been carried out for the case of one-dimensional Markov chain of atoms and for the case of the infinite-dimensional space.