Electric Field Gradient in Dilute B.C.C. Alloys. Application to Vanadium Alloys

Abstract

Abstract The formalism for the size effect electric field gradient (EFG) in dilute alloys with b.c.c. crystal structure is developed. The components of the stress field tensor F̃ are evaluated assuming dressed point ions interacting through the screened Coulomb potential. The size effect EFG is found cylindrically symmetric at the first and second nearest neighbour sites. The valence effect EFG is calculated using the transition metal model potential theory. It is assumed that due to quasilocalized d‐electrons, the shielding and antishielding mutually cancel in host region, however antishielding is accounted for in the outer region. The square well potential for the impurity in conjunction with Friedel's sum rule is used to evaluate the scattering phase shifts. The EFGs for dilute alloys of vanadium (V) with transition metal impurities Ti, Cr, Mn, Fe, Nb, and Ta are calculated. It is found that at both, the first and second nearest neighbour sites, the valence effect EFG is significantly larger than the size effect EFG. The calculated results for VTi, VNb, and VTa are in reasonable agreement with the experimental values.