Thermal Expansion of Rocksalt

Abstract

The microscopic Grueneisen parameters and the temperature dependence of the thermal Grueneisen parameter of NaCl are calculated from a shell model with six parameters, five of which are taken as pressure dependent. All parameters are determined from experimental elastic, optical, and dielectric data at absolute-zero temperature. The results agree within 6-8% with experimental data. The discrepancy is primarily attributed to the experimental error of the input data that are used to determine the parameters of the model. Calculations have also been made for two versions of the rigid-ion model (RIM) which indicate that the apparent success previously attributed to the Kellermann model is mainly due to cancellation of errors arising from omitting second-nearest-neighbor interaction and electronic polarizability.