Dependence of pressure on elastic, electronic and optical properties of CeO2 and ThO2: A first principles study

► Phase transition of CeO2 from fluorite to cotunnite-type structure at 28.9 GPa. ► Phase transition of ThO2 from fluorite to cotunnite-type structure at 29.8 GPa. ► The elastic constants and bulk modulus of CeO2 increase under pressure. ► The band gaps of CeO2 and ThO2 increase under pressure. ► The dielectric functions of CeO2 and ThO2 in cotunnite structure are calculated.