First-order effect of the extension of the perturbation around vacancies in metallic compounds

Abstract

We have performed self-consistent calculations of the electronic structure of single vacancies on both atomic sites in TAI (T≡Fe, Co or Ni). The potential perturbation on the first shell of neighbours in the host is included in this procedure, in a first-order perturbation model. Thus the diagonal elements of the cluster Green function are easily calculated and give the vacancy contributions and first-shell contributions to the total screening of the defect.

Our results fully justify the single-site model for vacancies in FeAl. The perturbation is more extended in NiAl, and too large in CoAl to be treated in first order on the first shell. This effect can be understood from the relative positions of the Fermi level with respect to the two d peaks of the density of states in these compounds.