Abstract: In the molecular dynamics study of the superionic conductor CaF_2, the structures of Ca~(2+) sublattice and F~- sublattice have been investigated based on the bond spherical harmonies method. The simulation temperatures are 1400, 1590 and 2000K and the pair potential used in the simulation is Born-Huggins-Mayer (BHM)potential. The bond order parameters Q_l have been calculated both for the computer-generated instantaneuos configurations from the simulation system and for the standard configurations from the normal distribution model of bond orientation. The comparison of Q_l between the molecular dynamics simulation and the normal distribution model shows that not only Ca~(2+) ions keep their original FCC frame stably, but in the F~- case there is a great deal of deformation at random from the original F~- sublattice.

Key words: CaF₂, Molecular dynamics simulation