The Importance of the Thermal Exchange-Correlation Effect for Properties of Shock-Compressed Fluid Helium*

Accurate knowledge of the material properties of H, He, and H–He mixtures across a wide range of thermodynamic conditions plays an important role in planetary science, astrophysics, and in the interpretation of high-energy-density physics experiments. Ab initio molecular dynamics simulations based on the free-energy density functional theory (DFT) have proven to be a successful and key tool to investigate materials including thermodynamic properties, transport properties, and phase transitions at extreme pressure and temperature conditions. The reliability of DFT predictions strongly depends on the accuracy of approximations for the exchange-correlation (XC) density functional. In this work, we employ the recently developed advanced thermal XC functional at the meta-GGA level of refinement¹ for the simulation of shock-compressed fluid He along the principal Hugoniot. Comparisons with results obtained using the standard ground-state XC functional demonstrate that the thermal XC effects play an important role in the accurate prediction and interpretation of experimental data.

1 V. V. Karasiev, D. I. Mihaylov, and S. X. Hu, Phys. Rev. B 105, L081109 (2022).