Exchange-correlation thermal effects in shocked deuterium: Softening the principal Hugoniot and thermophysical properties

Exchange-correlation (XC) thermal effects for transport and optical properties of deuterium along the principal Hugoniot are investigated. The study is performed using ab initio molecular dynamics simulations within the Mermin-Kohn-Sham density functional theory. XC thermal effects are taken into account via the temperature-dependent Karasiev-Dufty-Trickey generalized gradient approximation functional [V. V. Karasiev et al., Phys. Rev. Lett. 120, 076401 (2018)]. We find that XC thermal effects account for the softening of the Hugoniot at pressures P > 250 GPa and improve agreement with recent experimental measurements. Also, XC thermal effects lead to the reflectivity increase by about 2% for shock speeds above 20 km/s. The calculated reflectivity for shock speeds up to 50 km/s is in excellent agreement with recent experimental measurements on the Omega Laser System. The dc conductivity is increased by about 4% due to XC thermal effects. The system evolution along the Hugoniot crosses the so-called warm-dense-matter regime, and XC thermal effects must be taken into account to accurately predict the thermophysical properties across warm-dense conditions.