Electronic structure and covalency in superionic conductors

The electronic states of noble metal halides and alkali halides are calculated by the DVXα cluster method to get more microscopic evidence for the p — d hybridization and the covalency in noble metal halides. It is found that both components of anti-bonding and bonding exist in the diagram of overlap population (DOP) for AgX (X=halogen) and these two components are made up of the 4d band of Ag ion and the p band of halogen ion, which form the p — d hybridization. The covalency of noble metal halides is in the border between that of the fourfold coordinated compounds such as AgI and that of the sixfold coordinated compounds such as AgCl. These calculation results on the covalency are compared with the Phillips's ionicity. Paper presented at the Patras Conference on Solid State Ionics, Patras, Greece, Sept. 14 – 18, 2004.