Elastic And Ultrasonic Investigations Of Lanthanum Telluride Monocrystal At Elevated Temperature

The elastic energy density for a deformed crystal can be expanded as a power series of strains using Taylor's series expansion. For the face centered cubic crystal; one can get this expansion starting from nearest neighbor distance and hardness parameter utilizing Coulomb and Born Mayer potentials. The knowledge of the higher order elastic constants for a crystal is useful for obtaining the anharmonic properties of the crystals within the limit of the continuum approximation in a quantitative manner. The Lanthanum Telluride crystal possesses face centered cubic crystal structure. The theory is developed for obtaining second, third and fourth orders elastic constants (SOECs, TOECs and FOECs) of Lanthanum Telluride single crystals upto its melting point. With this theory SOECs, TOECs and FOECs of Lanthanum Telluride single crystals at an elevated temperature are evaluated. The data of SOECs, TOECs and FOECs are used to obtain the first order pressure derivatives (FOPDs) of SOECs and TOECs, second order pressure derivatives (SOPDs) of SOECs and partial contractions. Ultrasonic wave velocity and Ultrasonic wave attenuation give good insight to the crystal. The data of Lanthanum Telluride crystals obtained through different techniques give important and valuable information about internal structure and inherent properties of materials. The data thus obtained are compared with the experimental results whichever are available in literature.