An interionic potential was used to describe interactions in the fluoride. This was constructed from ab initio calculations. The potential was based upon formal ionic charges and included polarization effects which arose from the induced dipoles on both anions and cations. The cation polarization effects were shown to be important in explaining the observed differences between PbF2, and alkaline-earth fluorides of comparable cation size. In particular, lower transition pressures between the β- and α-phases, and qualitative differences between the shapes of the phonon dispersions for PbF2 and alkaline earths were reproduced. Simulations indicated a transition to a superionic conducting state in the β-phase, but this was at a temperature that was slightly higher than that observed experimentally. No ionic conduction was observed in the α-phase at comparable temperatures; in agreement with experiment. The pattern of diffuse neutron scattering, as predicted by simulations of the superionic domain, was shown to reproduce the distinctive intensity distribution which was experimentally observed.

M.J.Casliglione, M.Wilson, P.A.Madden: Journal of Physics - Condensed Matter, 1999, 11[46], 9009-24