Theory of charge perturbation due to impurities in transition metals

Abstract

The model wavefunction transformation is used to study the excess electronic charge density delta rho due to an impurity in a transition metal. The excess charge density is separated into two parts: one due to the non-nodal character of the model wavefunction and the other due to the depletion holes around the host ions. The former shows the Friedel oscillations modified by the bandstructure effects while the latter depends upon the nature of the conduction electrons in the vicinity of the ion cores of the host metal. For p and d electrons, the latter part of the excess charge density consists of an oscillatory part decreasing as 1/r3 and a part uniformly decreasing as 1/r3 which is due to the displacement of the charge centre in the effective core region from the nuclei. The various components of delta rho are calculated and compared. It is found that the excess charge density due to the depletion hole in the effective core region is larger by two orders of magnitude than the free electron part.