The　ionic　conduction　mechanisms　of　some　super　ionic　conductors,　alpha-AgI,　beta-Ag2S,　and　alpha-Ag2Se,　have　been　investigated　by　means　of　ab-initio　calculations　using　the　VASP　(Vienna　Ab-initio　Simulation　Package)　code.　Each　of　these　phases　has　a　BCC　(body-centered　cubic)　sub-lattice　formed　by　the　anions,　while　the　cations,　which　partially　occupy　the　12d　sites,　migrate　along　pathways　through　the　centers　of　the　faces　of　the　tetrahedra.　The　calculated　band　gaps　of　alpha-AgI,　beta-Ag2S,　and　alpha-Ag2Se　are　0.88　eV,　0.06　eV,　and　0　eV,　respectively,　which　implies　that　alpha-AgI　is　only　an　ionic　conductor,　whereas　beta-Ag2S　and　alpha-Ag2Se　are　mixed　electronic　and　ionic　conductors.　(C)　2008　Elsevier　B.V.　All　rights　reserved.