Dielectric Properties and Different Models of Ionic Crystals

Abstract
The dielectric properties of ionic crystals are discussed according to the various models so far proposed. To test Szigeti's relation on compressibility, the problem of the most suitable formula to account for the second-neighbor and many-body interactions is carefully discussed. Two different models for many-body interactions are considered. It is found that results are quite sensitive to the models of many-body interactions. From the corrected values of the Szigeti constant it is concluded that the shell model is good for some ionic crystals, while for others the deformation-dipole model may be better.