Molecular Dynamics Studies of Superionic Conductor CaF₂

Abstract

In the molecular dynamics study of the superionic conductor CaF₂, the ionic soft-core system, of which the pair potential consists of the Coulombic and soft-core potentials, is investigated. The influence of the potential, especially of the softness of the soft-core repulsion, on the distribution of anions and diffusion paths is studied. We also study the dynamics of the diffusion in comparison with those of α-AgI. Anions diffuse from a well-defined site to sites with strong correlation among neighboring anions. In contrast to the case of α-AgI, both the Coulomb and soft-core forces between anions are shown to be responsible for the diffusion. It is also shown that the vibrational properties of mobile and immobile ions are quite different from those of α-AgI.