Effective cluster interactions using the generalized perturbation method in the atomic-sphere approximation.

Abstract

We describe the generalized perturbation method in the atomic-sphere approximation (ASA) for calculating the effective cluster interactions. Based on our development of Korringa-Kohn-Rostoker coherent-potential approximation in the ASA [Singh et al., Phys. Rev. B 44, 8578 (1991)], the present approach is the next step towards developing a first-principles method that can be easily applied to describe substitutionally disordered alloys based on simple lattice structures as well as complex lattice structures with low symmetry. To test the accuracy of the ASA results, we have calculated the effective pair interactions (EPI) up to fourth-nearest neighbors for the substitutionally disordered ${\mathrm{Pd}}_{0.5}$${\mathrm{V}}_{0.5}$ and ${\mathrm{Pd}}_{0.75}$${\mathrm{Rh}}_{0.25}$ alloys. Our calculated EPI's are in good agreement with the respective muffin-tin results.