Theory of the electric-field gradient in dilute alloys.

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 [ital Al](Mg, Zn, Sn) and [ital 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.