Ab Initio Study of Mechanical and Vibrational Characteristics of Uranium Monoxide in Nuclear Reactor

In this research, the mechanical and phonon properties of UO in the rock-salt phase have been calculated systematically using density functional theory and ab-initio method in projector augmented wave pseudopotentials parameterization. The obtained lattice constant has good accordance with the experimental one at null pressure and temperature. The mechanical stability is confirmed because the positive elastic constants meet the Born-Huang criterion. The mechanical properties including bulk modulus, shear modulus, and Young’s modulus are evaluated using the Voigt-Reuss-Hill approximation. The value of Poisson’s ratio (v) is obtained to be nearly 0.36, which shows that this compound has an ionic bond and interatomic forces within the crystal are central. The elasticity analysis of the Kleinman parameter reveals that bond bending is dominant within the sublattice of UO. The vibrational density of states and phonon dispersion are investigated through the linear response approach. The results shows the dynamical stability of crystalline structure due to the inexistence of virtual frequencies in dispersion relations.