Theory of the electric-field gradient in dilute alloys.

Abstract

A unified theory of the electric-field gradient (EFG) in binary metallic alloys is proposed. The valence and size EFGs are generated simultaneously from crystal potentials for the perfect and imperfect lattices. Dielectric-screening theory is used to calculate the two-body potential and the crystal potential for dilute alloys. The anisotropy of the strain field is studied and it is found that the strain field becomes negligibly small beyond twenty-five nearest neighbors of the impurity. The EFGs are calculated at the displaced first- and second-nearest-neighbor positions without introducing any size strength parameter for Al(Mg, Zn, Sn) and Cu(Mg, Zn, Sn) alloys. The calculated values are found in good agreement with the experimental values. The valence EFG is dominant at the first-nearest neighbor while size EFG starts dominating at farther nearest neighbors.