ELECTRONIC-STATE AND COVALENCY IN NACL-TYPE ALKALI-HALIDE CRYSTALS

The discrete variational (DV) Xalpha cluster method has been used for investigations of the electronic state and bonding nature of alkali halide crystals. The bonding in these compounds which is considered to be typically ionic, contains covalent character to a certain extent. It is found that the covalency increases when the atomic number of halogen increases and that of alkali decreases. The ionic radius determined from the electronic charge density calculated deviates from Pauling's value, according to the extent of covalency.