The electronic and optical properties of ThO2 under pressure calculated by GGA plus U method

ThO2 (thoria) is an important semiconductor, optical material, and mineral. It has Fm 3-</mml:mover> m phase at normal pressure, and it transforms to the Pnma phase under high pressure. The electronic and optical properties of ThO2 are important and urgent to study for its applications. Since the exhaustive optical properties of ThO2 are scarce, we used the GGA+U method to calculate the electronic and optical properties of ThO2 at normal pressure as well as under high pressure in detail. Our calculated band gap of Fm <mml:mover>3<mml:mo>-</mml:mover> m phase increases with increasing pressure, while that of the Pnma phase nearly keeps constant. A blue shift in optical properties is found with increasing pressure. We discussed the relation between the band, the imaginary part of the dielectric function, and the density of states. We also used proper equations to fit the relation between band gap, absorption coefficient, and pressure. The acquired properties under pressure indicate phase transition as well as having application significance. Our studies not only stimulate the related researches but also pave a road for future application of ThO2 in the field of geosciences, physics, and materials.