Elastic and thermal properties of carbides of U, Pu, and Am

Abstract

In this study, we investigated the behaviors of three representative actinide monocarbides (AnCs, where An = U, Pu, and Am) in terms of their superior mechanical and thermo-elastic properties. Coulomb and Born–Mayer potentials were used to calculate the temperature-dependent second order and third order elastic constants up to the second nearest neighbor. The Voigt–Reuss–Hill approximation was employed to compute the values of Young's modulus (Y), Zener anisotropy ratio (A), shear modulus (G), bulk modulus (B), Poisson's ratio (σ), and Pugh's indicator (B/G) using second order elastic constants. The Born stability criteria and Vicker's hardness parameter (Hν) were analyzed to determine the strength and nature of the materials. The Debye average velocities and Breazeale's nonlinearity parameters were calculated in the temperature range from 100 to 500 K. Thermal properties such as the lattice thermal conductivity, thermal relaxation time, crystal energy density, and acoustic coupling constant were computed at different temperatures and along various directions. The longitudinal and shear components of ultrasonic attenuation were evaluated along the three crystallographic directions comprising <100>, <110>, and <111>. The temperature- and direction-dependent ultrasonic properties were correlated with other thermo-physical properties to extract important information such as the material strength and thermal conductivity in order to assess the microstructural quality and nature of the materials, which are useful for industrial applications.