Computer simulation of superionic CaF₂

Abstract

Rahman's molecular dynamics simulation (1976) of superionic CaF2, which is based on a rigid ion model has been simulated. Rahman's original analysis has been extended so as to bring out some important qualitative results not readily apparent from his published work. It is shown that the simulated system has the following features: (1) In spite of their very high mobility, the anions do not occupy the octahedral interstitial sites to any appreciable extent; (2) anion diffusion occurs by means of correlated hops predominantly in the (100) directions. These results, which are consistent with the conclusions drawn recently by Jacucci and Rahman (1978), are in strong contrast with the usual picture of diffusion in superionic fluorites.