Superionicity Study from Electronic State Calculation of Metal Halide Cluster

Abstract

The electronic states of silver halides and sodium halides are calculated by the DV-Xα cluster method to get more microscopic evidence for the p–d hybridization in noble metal halides. The calculations are carried out for the (A₁₃B₁₄)⁻ (A=Ag⁺ and Na⁺, B = halogen ion) clusters. 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⁺ and the p band of halogen ion, which form the p–d hybridization. On the other hand, the DOP of alkali halides is occupied by almost only bonding component. It is inferred that the origin of AgI type superionic conductor is in the weakness of p–d hybridization. The hypothetical rock-salt AgI is also discussed to investigate the unstableness of rock-salt AgI.