Advancing the Accuracy of DFT Simulations for High-Energy-Density Plasmas by Developing Temperature-Dependent Exchange-Correlation Functional*

Ab initio molecular dynamics simulations based on the free-energy density functional theory (DFT) has proven to be a successful and key tool to understand warm dense matter (WDM) and high-energy-density (HED) plasmas. DFT requires approximations for the exchange-correlation (XC) energy density functional, which effectively takes into account many-body interaction effects. Currently, vast majority of DFT simulations of WDM and HED plasmas use the ground-state XC functionals without explicit temperature dependence, leading to inaccuracy in the regime of T/T_F~0.5. In this talk we discuss development of XC density functionals with explicit temperature dependence based on rigorous constraints [1-3]. A simple but accurate scheme is implemented via universal additive thermal correction to XC using a perturbative-like self-consistent approach. The additive correction with explicit temperature dependence is applied to the ground-state deorbitalized strongly constrained and appropriately normed (SCAN-L) meta-GGA XC leading to thermal XC functional denoted as T-SCAN-L [4]. Incorporation of exact finite-temperature constraints makes functional accurate and broadly predictive over the entire temperature range. The T-SCAN-L meta-GGA functional shows significant improvement of accuracy for WDM and HED plasma simulations, when compared to traditional XC functionals, as demonstrated by the comparison to the reference path-integral Monte Carlo simulations for deuterium and helium equation of states. The T-SCAN-L calculations show good agreement with experimental measurements of the deuterium principal Hugoniot in the regime of maximum compression and sound speed. Direct current conductivity of warm-dense aluminum also gives better agreement with experiments over other XC functionals such as PBE and SCAN-L.