Temperature dependent physical effects of ultrasonic wave in beryllium chalcogenides

Temperature dependent physical effects of ultrasonic wave viz. ultrasonic attenuation due to interaction of sound wave and thermal phonons, thermoelastic loss and dislocation damping have been studied in beryllium chalcogenides (BeX, X = S, Se and Te) in the temperature range 50-500 K, along three crystallographic directions of propagation viz. [1 0 0], [1 1 0] and [1 1 1] for longitudinal and shear modes of propagation. Second and third order elastic moduli have been obtained using electrostatic and Born repulsive potentials and taking hardness parameter and nearest neighbour distance as input data. Gruneisen numbers, acoustic coupling constants and drag coefficients have been evaluated for longitudinal and shear waves along different directions of propagation and polarization. The results have been discussed and compared with the available data. It has been found that the temperature dependence of ultrasonic attenuation follows the temperature variation of diffusion coefficient and is mainly dominated by phonon-phonon interaction.