Cluster model electron lifetimes in dilute potassium alloys

Abstract

Anisotropic cluster model electron lifetimes are calculated for impurity scattering in the dilute potassium alloys K(Na) and K(Rb). The system is modelled by a finite cluster in free space. The largest cluster contains 35 scatterers corresponding to 4 BCC shells. An electron described with respect to a host cluster is scattered by an impurity cluster. An impurity cluster consists of a substitutional impurity surrounded by a number of possibly relaxed shells of host atoms. Only s and p scattering are accounted for. The phaseshifts used for the individual scatterers are taken from published APW fits as well as from potentials constructed in a standard way. It is found that the average lifetime for both alloys has the right order of magnitude. Further p scattering contributes significantly for the case of K(Rb). The anisotropy of the inverse lifetimes is very dependent on cluster size and does not converge when the cluster size increases.