Electronic structures and mechanical properties of uranium monocarbide from first-principles LDA+ULDA+U and GGA+UGGA+U calculations

The electronic structure, elastic constants, Poisson's ratio, and phonon dispersion curves of UC have been systematically investigated from the first-principles calculations by the projector-augmented-wave (PAW) method. In order to describe precisely the strong on-site Coulomb repulsion among the localized U 5f   electrons, we adopt the local density approximation (LDA)+U(LDA)+U and generalized gradient approximation (GGA)+U(GGA)+U formalisms for the exchange correlation term. We systematically study how the electronic properties and elastic constants of UC are affected by the different choice of U as well as the exchange-correlation potential. We show that by choosing an appropriate Hubbard U   parameter within the GGA+UGGA+U approach, most of our calculated results are in good agreement with the experimental data. Therefore, the results obtained by the GGA+UGGA+U with effective Hubbard parameter U chosen around 3 eV for UC are considered to be reasonable.