SHELL-MODEL MOLECULAR-DYNAMICS SIMULATION OF SUPERIONIC CONDUCTION IN CAF2

We have developed a new code for performing molecular dynamics simulations of ionic materials, in which electronic polarization is included via the shell model. Key features of the method are the use of the conjugate-gradients technique for relaxing the shells at each step, and a new device for ensuring energy conservation. The new code is used to study superionic conduction in CaF2, which has previously been studied by conventional rigid-ion molecular dynamics. For both static and dynamic quantities, the modifications caused by explicit inclusion of electronic polarizability are remarkably small.