Interionic pair potentials in the alkali metal halides

Abstract

A generalised pair potential of the form (in reduced units)ϕ(r)= [graphic omitted] –ar^–4–r^–1 has been used to parametrise experimental data for gaseous alkali metal halide ion pairs. The repulsive term is found to be “harder” than is commonly used in semi-empirical effective pair potentials from crystal data. The derived values of a and computations of crystal properties, without the ar^–4 term in the pairwise additivity approximation, accord with a simple polarisable ion model.