First-principle study on structural and electronic properties of CeO2 and ThO2 under high pressures

High-pressure structural and electronic properties of CeO2 and ThO2 are investigated with density functional calculations. An isostructural phase transition with space group Pnma at about 100 GPa has been observed in both compounds. The high-pressure Pnma phase is revealed as being an orthorhombic distortion of the hexagonal Ni2In structure. A pressure-induced metallization in the high-pressure Pnma phase with a mechanism of Wilson transition is also predicted at around 250 GPa in CeO2, and at 350 GPa in ThO2, respectively. Two new metallic phases with space group P (3) over bar m1 and I4/mmm are found as the ground state in CeO2 when pressure is above 450 GPa, whereas in ThO2 the Pnma phase is stable up to 1 TPa. The equations of state are analyzed, as well as the pressure dependence of the lattice parameters, atomic fractional coordinates, and electronic band gaps.