Dynamic properties of mobile Cu ions in the superionic conductor were studied using ab initio simulations. The gross charge of each ion and the overlap population between each Cu-I pair were calculated using population analysis as a function of time. It was shown that covalent bonding around the Cu ions weakened when they diffused in the octahedron cage during migration between neighboring tetrahedral sites. It was also shown that the ionicities of Cu ions at octahedral sites were greater than those of Cu ions at tetrahedral sites. The results clearly revealed that the time evolution of local bonding played an important role in imparting high ionic conductivity.

Diffusion of Mobile Ions and Bond Fluctuations in Superionic Conductor CuI from ab initio Molecular-Dynamics Simulations. Shimojo, F., Aniya, M.: Journal of the Physical Society of Japan, 2003, 72[11], 2702-5