First principles modeling of zirconium solution in bulk UO₂

We modeled the solution behavior of zirconium in uranium dioxide (UO ₂) by using density functional theory. The Coulomb repulsion of uranium 5f elections was characterized by a spherically averaged Hubbard parameter. Our results indicate that zirconium prefers to locate at U vacancies in UO₂ and presents a slight tendency to accumulate in thermodynamics. The solution energies for hcp Zr metal and monoclinic ZrO ₂ indicates that these two precipitates are insoluble in UO ₂. In perfect UO₂, the band-gap opening is governed by U 5f peaks around the Fermi energy, whereas the solution of zirconium further leads to the band gap splitting owing to the introduction of zirconium 4d peaks especially at high defect concentrations.