Mode-Grüneisen Parameters and Thermal-Expansion Coefficient of NaCl, CsCl, and Zinc-Blende-Type Crystals

Abstract

The temperature dependence of the coefficient of thermal expansion of a number of ionic and partially ionic crystals is calculated using a modified rigid ion model and a shell model of lattice dynamics. The model parameters are obtained from long‐wavelength optic mode frequencies, elastic constants and the high‐and low‐frequency dielectric constants. Using the pressure derivatives of these quantities, mode‐Grüneisen parameters as functions of wave vectors are next obtained. Thermal expansion coefficient is calculated from the Grüneisen parameters in the quasiharmonic approximation. The calculated values compare well with experimental data.