Temperature Dependent Anharmonic Properties of Alkali Cyanide Crystals

Abstract

A new method has been developed for calculating the temperature dependence of enharmonic elastic properties of alkali cyanide crystals using the concept of phonon pressure. An interionic potential which consists of the long-range Coulombian, van der waals dipole-dipole and dipole-quadrupole and three body interactions. Hafemeister-Flygare type short-range overlap repulsive potential is taken in to account up to the second neighbor ions. The thermal effects and enharmonic properties of alkali cyanide crystals have been investigated for the first time. Calculated valves of cohesive energy consisting the vibrational term are found in good agreement with the experimental values. Six third order elastic constants have also been calculated for NaCN, KCN and RbCN cr.