SCAN-L extended to an exchange-correlation free-energy density functional for extreme conditions

The predictive potential of density functional theory (DFT) for simulation of systems under extreme conditions of temperature and pressure depends crucially on having an exchange-correlation (XC) free-energy functional that is accurate for such state conditions. Distinct from zero-temperature XC functionals, the XC free-energy functional must have an explicit temperature dependence. Recently, that has been achieved for the local density approximation [“KSDT”, Phys. Rev. Lett. 112, 076403 (2014) ] and generalized-gradient approximation [“KDT16”, Phys. Rev. Lett. 120, 076401 (2018) ].

By use of the systematic construction scheme of the KDT16 GGA, we extend the recent SCAN-L ground-state orbital-free meta-GGA XC functional [Phys. Rev. A 96, 052512 (2017), Phys. Rev. B 98, 115161 (2018)] to a semilocal XC free-energy functional. This completes the ladder of computationally efficient orbital-free free-energy XC functionals. The accuracy of the new SCAN-LF in the warm dense matter regime is assessed and compared to KSDT and KDT16.