Calculation of the Optical Constants for the Potassium Halides from Korringa-Kohn-Rostoker Energy Bands

KKR energy bands are used to calculate joint densities of states for KCl, KBr, and KI between conduction states and valence and core states by means of a simple interpolation scheme. The results are discussed and compared with experimental spectra in the vacuum ultraviolet and soft-x-ray regions. An overall agreement between theory and experiment is found which suggests that strong exciton effects are present in excitations from $p$-like valence bands, but not from $d$ bands.