Acoustical dissipation due to phonon‐phonon interaction, thermoelastic loss and dislocation damping in MnO and CoO

Abstract

The temperature dependent acoustical dissipation due to phonon‐phonon (p‐p) interaction, thermo‐elastic mechanism and dislocation damping due to screw and edge dislocations have been evaluated in MnO and CoO in fcc (NaCl‐B1 type) phase, in a wide temperature range 50 ⩽ T ⩽ 500K for longitudinal and shear modes of propagation along three crystallographic directions viz. <100>, <110> and <111>. Electrostatic and Born repulsive potentials were used to obtain second order and third order elastic constants (SOEC and TOEC), taking interactions up to next nearest neighbours.The SOEC and TOEC obtained at diffrent temperatures have been used to obtain gruneisen parameters and non‐linearity or anisotropic parameters which in turn were used to evaluate (α/f2) for longitudinal and shear waves. Specific heat (as function of Debye temperature), hardness parameter, lattice parameter have been used as input data. It has been found that (α/f2) increases with temperature and the acoustical dissipation is mainly influenced by p‐p interaction.The possible implications of results have been discussed.