Meta-GGA exchange-correlation free energy density functional to increase the accuracy of warm dense matter simulations

Abstract

We discuss strategies for thermalization of the ground-state meta-generalized gradient approximation (meta-GGA) exchange-correlation (XC) functionals. A simple but accurate scheme is implemented via universal additive thermal correction to XC using a perturbativelike 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 a thermal XC functional denoted here as T-SCAN-L. The thermal T-SCAN-L meta-GGA functional shows significant improvement in density functional theory calculation accuracy for warm dense matter by a factor of 3 to 10, achieving an accuracy of total pressure between a few tenths and $\ensuremath{\sim}1$% when compared to traditional XC functionals, as demonstrated by the comparison to path-integral Monte Carlo simulations for helium equation of state. The T-SCAN-L calculations of dc conductivity of warm dense aluminum also give better agreement with experiments over other XC functionals such as PBE and SCAN-L.