First Principles Calculations of the Equation of State of MgSiO₃ in the Gigabar Regime

The equation of state (EOS) of silicates at extreme conditions is of significant interest in planetary science and high-pressure physics. Using path integral Monte Carlo (PIMC) and density functional theory molecular dynamics (DFT-MD) simulations, we study the properties of MgSiO₃ enstatite in the regime of warm dense matter. We generate a consistent equation of state for MgSiO₃ over a wide range of temperature and density conditions, ranging from 10⁴ to 10⁸ K and 0.1- to 20-fold the ambient density. An analysis of the structural and thermodynamic properties of the liquid is provided as L and K shell electrons are ionized with increasing temperature and pressure. The shock Hugoniot curve, that we derived from our EOS, is in very good agreement with the experimental data available for megabar pressures. In the gigabar regime, shock experiments are predicted to reach maximal compression. We analyze the shape of the Hugoniot curve under these conditions and demonstrated that the shock compression is controlled by the ionization of L and K shell electrons of the three nuclei.