Molecular dynamics simulation of superionicity in neighborite, NaMgF3

Superionicity in neighborite, NaMgF3, has been studied by molecular dynamics using parameter-free Gordon-Kim potentials. These simulations show that this halide-based perovskite has a superionic phase. The onset temperature for superionicity is similar to 50-100 K below the melting point. This is a novel type of superionicity in a halide, occurring as it does in a perovskite rather than a fluorite. Superionicity is demonstrated to occur whether one uses the full ionicity for Mg2+ and F- or employs reduced charges derived from a Quantum Chemistry calculation. The relevance of these findings to predictions of superionicity in the oxide perovskite MgSiO3 [Matsui and Price, 1991] is discussed.