Ab initio study of the 57 Fe electric field gradient in (FeAl)1-xTx(T=3d element) dilute alloys with B2-type structure

Abstract

We present an ab initio study of the electric field gradient at Fe nuclei in the series of (FeAl)1¡xTx dilute alloys with B2-type crystal structure. The ternary additions T, of concentration x ¼ 0:06, from the group of 3d-type transition metals (Ti, V, Cr, Mn, Co, Ni, Cu) are considered. Lattice, local valence electron (3d, 4p) and weakly bound 3p core electron contributions to electric field gradient are separated out and discussed in the context of the T-atom site preference and changes of the electronic structure upon alloying. Contrary to earlier reports, we found that for most Fe nuclei the dominant contribution comes from the d-type valence electrons cancelled partially by the 3p and 4p electric field gradients which are both of opposite sign to that of the 3d one. The shielding effect of 3p semicore electrons is found and related to the electric ¯eld gradient contributed by the local valence electrons.