Screened hybrid and DFT + U studies of the structural, electronic, and optical properties of U3O8.

A systematic comparison of the structures and electronic and optical properties of U(3)O(8) in the c2mm, P62m, and P21/m structures (the α, β, and γ phases, respectively) is performed using density functional theory + U (PBE + U) and the Heyd-Scuseria-Ernzerhof screened hybrid functional (HSE). The relationship between the semiconducting C2mm phase of U(3)O(8) and the high temperature, metallic P62m phase is explored in more detail. Our calculated results show that the HSE functional gives a better description of the electronic and optical properties when compared with available experimental data for the α and β phases, but neither approach does particularly well for the high pressure γ phase.