Anisotropic relaxations introduced by Cd impurities in rutile TiO₂: First-principles calculations and experimental support

Abstract

We present an ab initio study of the relaxations introduced in TiO₂ when a Cd impurity substitutes a Ti atom and an experimental test of this calculation by a perturbed-angular-correlation (PAC) measurement of the orientation of the electric-field gradient (EFG) tensor at the Cd site. The ab initio calculation predicts strong anisotropic relaxations of the nearest oxygen neighbors of the impurity and a change of the orientation of the largest EFG tensor component, V_(33) , from the [001] to the [110] direction upon substitution of a Ti atom by a Cd impurity. The last prediction is confirmed by the PAC experiment that shows that V_(33) at the Cd site is parallel to either the [110] or the [1͞10] crystal axis.