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.