New approximation in the electronic theory of disordered alloys

A multiple-scattering theory of binary disordered alloys is presented using a single-site approximation in a form different from that of the coherent-potential theory. A reference Hamiltonian and its propagator are defined by the requirement that there be no forward scattering in this reference frame. The reference Hamiltonian is periodic with the periodicity of the lattice. The resultant solutions are self-consistent and have the advantage of permitting one to directly calculate the various matrix elements, both diagonal and nondiagonal, of the alloy propagator. The formalism is not limited to a single-band model Hamiltonian nor to localized perturbations, but has wide applicability. The limitations of the approximations and idealizations made in this theory are discussed, especially the neglect of a self-consistent treatment of the potential perturbations.