EHT calculation of the electronic states for the ionic crystals

The cluster model calculations of the electronic structure for the ionic crystals (LiF, NaCl and KCl) are carried out by means of the charge self-consistent Extended Huckel Theory (EHT) including the Madelung Potential. The results show that the 6 x 6 x 6 cluster can be used to simulate the real crystal. The calculated band gaps and the widths of the valence bands are in good agreement with the experimental data. The total and local density of states display the presence of the surface states in the band gap. The contribution to the surface states are almost all from the alkali atoms at the surface. The surface states near the bottom of the conduction band are essentially from the s state and a part of p state of the alkali atoms at the surface