Feasibility of cluster calculations in describing impurities in simple metals

Abstract

The spin-density-functional formalism has been applied to study electronic properties of small spherical clusters of an ideal free-electron metal (jellium). The electronic structure of a hydrogen atom embedded in the center of the cluster has been calculated as a function of the cluster size. A comparison of the results to the exact limit of the hydrogen atom in an infinite jellium shows that a large cluster size (about 100 atoms) is needed for an accurate description of the electronic structure of the impurity. Self-consistent unrestricted Hartree-Fock calculations have been performed for small Li clusters with a hydrogen impurity, and the results are compared with those of the jellium model. As an effect of the finite cluster size, both calculations show similar features in the cluster properties. Methods for calculating the impurity Knight shift using the cluster technique have been studied.