Analysis of the Transport Properties of Alkaline-earth Halides MX₂ (M = Ca, Sr, Ba, and X = F, Cl, Br) by Simulation with a Polarizable Ion Model

Abstract

A polarizable ion model was applied to the solid and molten alkaline-earth halide MX₂, the parameters of which were determined by using first-principles calculations based on density functional theory, where M = Ca, Sr, Ba, and X = F, Cl, Br. The obtained parameters were used to evaluate the ionic conductivity, shear viscosity, and thermal conductivity in the molten and solid states by molecular dynamics simulations using the Green-Kubo relations. The calculated results were in good agreement with the experimental ionic conductivities and shear viscosities. The behaviors of all the calculated properties were well accounted for by ionic mass, number density, and packing fraction. Especially, the calculated thermal conductivities were well expressed by the empirical formula obtained for molten alkali halides. In addition, it was revealed that the reversal of cationic dependence in ionic conductivity of fluorides between solids and melts is due to the mass effects of carrier ions.