Sound Attenuation at High Temperatures in Pt

Ultrasonic attenuation due to phonon-phonon interaction and thermoelastic loss was evaluated in VIII group transition metal Pt in a wide temperature range (100 K to 1500 K) for longitudinal and shear waves along〈100〉, 〈110〉 and〈111〉 directions and for shear waves polarised along different directions. Electrostatic and Born-Mayer potentials were used to obtain second and third order elastic constants, taking nearest-neighbour distance and hardness parameter as input data. Second and third order elastic constants data obtained at different temperatures were used to obtain Gruneisen parameters and non-linearity or anisotropy parameters which in turn were used to evaluate (α/f$\text{}^{2}$)$\text{}_{l}$ and (α/f$\text{}^{2}$)$\text{}_{s}$ in Akhiezer regime. The results were discussed and it was found that at lower temperatures (α/f$\text{}^{2}$) increases rapidly with temperature and then rate of increase becomes very small. Contribution to the total attenuation due to thermoelastic loss is negligible so that due to phonon-phonon interaction establishing that major part of energy from sound wave is removed due to interaction with thermal phonons (lattice vibrations).