Ultrasonic Grüneisen parameter for nonconducting cubic crystals

Abstract

The effective ultrasonic Grüneisen parameter obtained from room temperature measurements of the attenuation in 12 cubic crystals is compared with calculations for the anisotropic elastic continuum model in terms of second- and third-order elastic constants. The agreement between the calculated values and those derived from the ultrasonic attenuation is in most cases within a factor of 2 provided local equilibrium effects are included in the expression for the attenuation coefficient. The model accounts in general for the anisotropy and polarization dependence of the attenuation and can be used to estimate the magnitude of the sound absorption by acoustic thermal phonons from known elastic and thermal properties. Ultrasonic Grüneisen parameters are smallest for shear waves polarized along <001≳. Crystals with the NaCl structure show a larger and more anisotropic mean anharmonicity than covalent crystals and alkaline earth fluorides.