Phase transition and thermodynamics of thorium from first-principles calculations

We report on the first-principles study of the phase transition and thermodynamic properties of the thorium metal (Th) within the framework of quasiharmonic approximation. The structural properties of Th under pressure are well reproduced. It is found that the fcc–bct phase transition occurs at 70 GPa. Based on our calculated phonon dispersion curve that is in good agreement with experiment, the thermal equation of state and thermodynamic properties, such as thermal pressure, heat capacity and entropy are obtained. All the properties of Th under high pressure and high temperature are predicted successfully.