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

By using density functional theory and the ab initio method for projector augmented wave pseudopotential parameterization, the mechanical and phonon properties of UO in the rock-salt phase have been systematically calculated. At null pressure and temperature, the obtained lattice constant is in good agreement with the experimental one. Mechanical stability is confirmed because the positive elastic constants meet the Born-Huang criteria. 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 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 substructure of UO. The vibrational density of states and phonon dispersion are investigated through the linear response approach. The results show the dynamical stability of crystalline structure due to the inexistence of virtual frequencies in dispersion relations.