Photoelastic behaviour and interionic potentials in alkali halide crystals

In order to make a critical test of some recently developed interionic potentials based on the shell model, the photoelastic behaviour of the alkali halide crystals has been investigated. Values of the strain derivatives of the static and high-frequency dielectric constants have been calculated from sets of potentials due to Catlow et al., Sangster et al., and Sangster and Atwood. A comparison of the results obtained with available experimental photoelastic data demonstrates the superiority of the second set of potentials of Catlow et al.