Molecular dynamics simulation of fast-ion conduction in SrCl₂. I. Self-diffusion

Molecular dynamics simulations have been performed in order to study fast-ion conduction in solid SrCl 2 over a range of temperatures and densities. The simulations are carried out on a system of 324 ions interacting through rigid-ion potentials. The anion diffusion constant increases from a very small value to a value typical of molten salts over a temperature range of about 200K, in qualitative accord with experiment, but the transition temperature is about 20% higher than the experimental one. Analysis indicates that diffusion occurs by discrete hops between regular lattice sites, the ion residence time being an order of magnitude greater than the flight time. The diffusion can be described in terms of the motion of vacancy and interstitial defects. The concentration of defects above the transition temperature is approximately 3% of vacancies per regular site.