Generalized perturbation theory in disordered transitional alloys: Applications to the calculation of ordering energies

Abstract

Ordering effects in disordered alloys are studied by means of a generalized perturbation method. The unperturbed state is taken to be the completely disordered state treated in the coherent potential approximation. Explicit formulae are given for the variations of the electronic energy and of the densities of states induced by partial long- and short-range orders. The validity of the perturbation expansion is discussed in relation to the possible existence of a small parameter and the results are compared with those provided by the usual phenomenological models involving pair interactions.