Electric-field gradients in dilute Cu alloys: The role of the Cudelectrons

The electric-field gradients induced by 3d and 4sp impurities on neighboring Cu atoms are calculated with use of local-density-functional theory and a recently developed full-potential Green's-function method. We find that the dominant contribution arises from the Cu d electrons, in particular from unoccupied antibonding d states on the Cu sites formed by hybridization with the impurity states. All previous calculations, strongly relying on jellium models, completely fail to describe this effect.