Unprecedented accuracy of the equation of state and band-gap closure dynamics of warm dense krypton from first-principles calculations*

The thermodynamical and electric properties of warm dense krypton are crucial to accurately model the nuclear reactor process and understand the planet’s structure and dynamics. Using recently developed thermal exchange-correlation (XC) density functionals, meta-GGA level T-SCAN-L, and hybrid KDT0, we perform fully consistent density functional theory molecular dynamics (MD) simulations to explore the equation of state and optical properties of krypton in density and temperature range of 2.6 to 8.0 g/cm³ and 1 to 60 kK, respectively. Because of its high susceptibility to equation-of-state data, sound speed along the principal Hugoniot is used to validate and benchmark T-SCAN-L. We demonstrate that the inclusion of inhomogeneity and thermal XC effects via T-SCAN-L leads to much better agreement with the experimental result that has so far been unattainable by any theoretical model. The insulator-metal transition is investigated with the use of the Kubo–Greenwood formalism in combination with MD snapshotting. Reliable ionic configurations obtained from MD simulations utilizing T-SCAN-L and electronic structures with a realistic band gap predicted by KDT0 contribute to significant improvement in dc conductivity compared to previously published results.