Electronic and optical properties of (U,Th)O2 compound from screened hybrid density functional studies

• We use the HSE method to study the (U,Th)O2 mixed oxide.
• The HSE method can reproduce band gaps for UO2 and ThO2 simultaneously.
• The optical properties for the (U,Th)O2 mixed oxide are presented.
• The optical properties for (U,Th)O2 are compared with UO2 and ThO2.

The electronic structure and optical properties for the (U,Th)O2 compound are systematically studied by employing the Heyd–Scuseria–Ernzerh method (HSE) of screened hybrid density functional. The electronic band gap of (U,Th)O2 is predicted to be 3.06 eV, in the middle of the values of UO2 and ThO2. Based on wavefunction analysis, we conclude (U,Th)O2 to be a Mott insulator in its ground state. The frequency dependent dielectric functions and optical properties are then calculated and compared with those of ThO2 and UO2. At the visible light frequency range, the adsorption coefficients for ThO2, UO2 and (U,Th)O2 are totally different, which gives an accessible method to predict the proportion of U atoms in an arbitrary unknown (U,Th)O2 compounds from the adsorption spectrum of visible lights.