Variation of electronic state of AgI-based superionic conductors with movement of Ag ions

The electronic state of AgI-based superionic conductors was calculated by the DV-Xα cluster method. A model cluster, derived from the α-AgI crystal structure, was used. An Ag ion in the cluster was moved from a tetrahedral site to another tetrahedral site through a neighboring octahedral site. The electronic state of the same model cluster for Na ion was also calculated for comparison. The total bond order between the moving Ag ion and the other ions was decreased with the movement of the Ag ion and was slightly increased at the center of the octahedral site. The change of the total bond order of the Ag ion, however, was much smaller than that of the Na ion. This smaller change of the total bond order of the Ag ion should be one of the origins of the fast movement of Ag ions in AgI-based superionic conductors.