First-principles study of electronic structure and insulating properties of uranium and plutonium dioxides

First-principles density functional theory calculations were carried out to investigate the electronic structure and the degree of 5f states localization of the Mott-Hubbard type insulators UO₂ and PuO₂. We used the fully relativistic cluster discrete variational method (RDV) with the local exchange-correlation potential. The energies of one-electron transition between occupied and vacant 5f^5/2 states of neighboring actinide atoms were evaluated on the base of the ground state and the excited state calculations. It is found that in UO₂ and PuO₂ the energy difference between 5f^5/2 levels of nearest metal sites in the lattice are close to 1.0 eV and 0.9 eV, despite the results of conventional band structure approach predicting that both oxides are good conductors.