Pair correlation functions, anion-density distribution and fluoride-ion diffusion in Ba1-xGdxF2+x solid solutions were investigated, over a temperature range which included the superionic transition, by molecular dynamics simulation using Born-Mayer-Huggins pair potentials. According to the simulation results for x > 0.1, both the 4b (cubic-site symmetry) and 48i positions accommodated fluorine interstitials (Fi-). Below the superionic transition, the migration of F- ions at low doping levels was dominated by non co-linear jumps between lattice and interstitial sites. Computer simulations confirmed that trigonal Gd3+-Fi- dipolar complexes predominated over tetragonal complexes. It was shown, using Monte Carlo simulation, that rare-earth ions in the solid solutions had a tendency to aggregate.

Molecular Dynamics Simulations of Ba1-xGdxF2+x Solid Solutions over a Wide Temperature Range: II. Structural Characteristics and Fluoride Ion Diffusion. Gotlib, I.Y., Murin, I.V., Piotrovskaya, E.M., Brodskaya, E.N.: Inorganic Materials, 2003, 39[3], 291-8