The dynamic and electronic properties of mobile ions in the superionic conductors CuI and Ag2Se are studied by means of ab initio molecular dynamics simulations. The superionic behavior of these materials is successfully reproduced by our simulations. To investigate the bonding nature of these materials, the spatial distributions of the electrons and the time evolutions of the gross charge of the ions are calculated by the population analysis method. The time evolution of the electronic states around the mobile ions indicates that the local chemical bonding properties change accompanying the diffusive motion of mobile ions. It is also shown that the 4p-electron populations of Cu in CuI and 5p-electron populations of Ag in Ag2Se change largely with time, while the s- and d-electron populations depend weakly on time. (c) 2006 Elsevier B.V. All rights reserved.