Magnesium oxide at extreme temperatures and pressures studied with first-principles simulations

Area of Science:

• Condensed matter physics
• Planetary science
• Plasma physics

Background:

• Understanding the equation of state for materials like MgO is crucial for modeling extreme environments.
• Warm dense matter conditions bridge the gap between classical and quantum physics.

Purpose of the Study:

• To determine the equation of state of magnesium oxide (MgO) under warm dense matter conditions.
• To investigate the electronic structure and ionization mechanisms of MgO at high densities and temperatures.
• To compare MgO's shock compression behavior with that of pure oxygen.

Main Methods:

• Combining path integral Monte Carlo and density functional theory molecular dynamics simulations.
• Simulating MgO across densities from 0.35 to 71 g cm⁻³ and temperatures from 10,000 K to 5 × 10⁸ K.

Main Results:

• Observed hybridization of L-shell orbitals in magnesium and oxygen at high densities, leading to gradual ionization.
• Identified unique shock Hugoniot curve for MgO, differing from oxygen's curve due to distinct compression maxima.
• Predicted a maximum compression ratio of 4.66 at 6.73 × 10⁷ K for MgO.

Conclusions:

• MgO exhibits distinct electronic and compression properties compared to pure oxygen under extreme conditions.
• The study provides critical data for astrophysical and inertial confinement fusion research.
• Investigated the potential of multiple shocks and ramp waves for exploring wide density-temperature ranges.