First-principles calculations to investigate phonon dispersion, mechanical, elastic anisotropy and thermodynamic properties of an actinide-pnictide ceramic at high pressures/temperatures

Abstract

The actinide-pnictide ceramic materials have attracted great research attention owing to their fundamental and applied prospects in view of modern technological interest in materials engineering, ceramic and energy industry, and domestic usage. In this article, we report on the calculated structural, mechanical, dynamical, and thermodynamic properties of a first time theoretically designed model actinide-pnictide ceramic material, UP. For the high pressure/temperature calculations of the target properties, we employed density functional theory based first-principles procedure within GGA density functional. The computed results suggest that the experimental lattice constant is congruence with our estimated value. The calculated elastic coefficients are positive and satisfied Born-Huang criteria, thus revealing the mechanical stable structure of this ceramic material. The obtained Poisson’s ratio is approximately 0.28, implying the ceramic is ionic having central interatomic forces. The evaluated value for Kleinman parameter is 0.21, implying the presence of a bond bending. The phonon dispersion and density of state curves are computed using density functional perturbation theory. The results reveal the absence of virtual frequencies in the vibrational spectrum, confirming the dynamical stability of the crystalline structure. The thermodynamic properties calculated at elevated pressures and temperatures through Debye’s quasi-harmonic model, include Grüneisen parameter, Debye temperature, thermal expansion, entropy, isothermal bulk modulus, isochoric heat capacity. It is found that entropy is more sensitive to pressure at high temperatures.

Keywords

• Ceramics
• First-principles
• Rare earth metals
• Elastic coefficients
• Thermodynamic properties
• Debye temperature