Relativistic Electronic Structure of KI Crystal

Abstract

Energy bands in KI are calculated by means of the relativistic Green's function method. In setting up the potential, one parameter is used so that the gap energy agrees with the observed value. It is found that the highest filled band is completely split off into a couple of bands on account of the strong spin-orbit interaction. Both the top of the valence band and the bottom of the conduction band are located at the point k =0. The d bands which originate from the atomic 3 d states in the K + ions lie just above the lowest s -like conduction band. The results are discussed with reference to recent experimental information. It is suggested that the d bands centered on the alkali ions are responsible for the extra excitons observed in potassium and rubidium halides.