Neutron diffraction measurements were made of the rock-salt phase, at high pressures and temperatures, with regard to the structural disorder which was associated with high conductivity. In contrast to the first-order structural phase transition which led to a fast ionic conducting -phase at ambient pressures, the fast ionic behavior in the rock-salt phase occurred above a diffuse transition, with a small anomaly in lattice parameter and a continuous increase in the occupation of interstitial tetrahedral sites with increasing temperature. There were some 10 times more defects in the fast ionic phase of the rock-salt phase than in the isostructural AgBr at ambient pressures and 1K below the melting point.

D.A.Keen, S.Hull, W.Hayes, N.J.G.Gardner: Physical Review Letters, 1996, 77[24], 4914-7