Ultrasonic attenuation in rare-earth monoarsenides

Abstract

The present paper deals with the theoretical calculation of mechanical and thermophysical properties of rare-earth monoarsenides, XAs (X: Np, Pu, Th and U) using elastic constants as the input parameters. These second- and third-order elastic constants (SOECs and TOECs) are determined in the temperature range 100–500 K using Coulomb and Born–Mayer potential upto second nearest neighbours. In order to provide the link between mechanical and dynamical behaviour of crystals, parameters such as Young’s modulus, bulk modulus, Poisson’s ratio etc. are also calculated. In addition, the Cauchy relationship is obeyed by the chosen monoarsenides and are fairly anisotropic, which results in the measurement of longitudinal and shear wave velocities along 〈1 0 0〉, 〈1 1 0〉 and 〈1 1 1〉 directions. The toughness/fracture (G/B T) ratio is greater than 0.60, which implies that XAs compounds are brittle at room temperature. Further, the Debye temperature is computed using Debye average velocity as the input parameter. It helps in the characterization of lattice vibrations of a solid. In this work, ultrasonic attenuation due to phonon–phonon interaction (α/f 2)p−p and thermoelastic loss (α/f 2)th are computed for XAs from 100 to 500 K using Mason’s theory. It further helps in evaluating the microstructural properties of the chosen materials. The obtained results indicate that XAs is mechanically stable and are compared with data available in the literature.