Ab initio anharmonic thermodynamic properties of cubic CaSiO3 perovskite

We present an $\\textit{ab initio}$ study of the thermodynamic properties of\ncubic CaSiO$_3$ perovskite (CaPv) over the pressure and temperature range of\nthe Earth's lower mantle. We compute the anharmonic phonon dispersions\nthroughout the Brillouin zone by utilizing the phonon quasiparticle approach,\nwhich characterizes the intrinsic temperature dependence of phonon frequencies\nand, in principle, captures full anharmonicity. Such temperature-dependent\nphonon dispersions are used to calculate $\\textit{ab initio}$ free energy in\nthe thermodynamic limit ($N \\rightarrow \\infty$) within the framework of the\nphonon gas model. Accurate free energy calculations enable us to investigate\ncubic CaPv's thermodynamic properties and thermal equation of state, where\nanharmonic effects are demonstrated. The present methodology provides an\nimportant theoretical approach for exploring phase boundaries, thermodynamic,\nand thermoelastic properties of strongly anharmonic materials at high pressures\nand temperatures.\n