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.