Application of the Orthogonalized-Plane-Wave Method to Lithium Chloride, Sodium Chloride, and Potassium Chloride

The orthogonalized-plane-wave method has been used to compute the energy bands of LiCl, NaCl, and KCl. General results are obtained that are valid for any diatomic lattice. Computer programs (which considerably reduce the labor of applying this method to a wide class of substances) have been developed and are discussed. The results are compared with those of recent calculations and experiments. In general, there seems to be a good correlation between the present results and those of experiment. It is suggested that the peculiar optical absorption of LiCl may be due to transitions from the valence band to the conduction band involving the line $\Lambda$ and the point $L$ in the Brillouin zone. The possibility of $X$ excitons in NaCl and LiCl is explored.