Nonempirical generalized gradient approximation free-energy functional for orbital-free simulations

We report a purely nonempirical generalized gradient approximation for the noninteracting free energy functional of orbital-free density functional theory obtained via a novel constraint-based parametrization scheme. We use that functional to provide forces for finite-temperature molecular dynamics simulations in the warm dense matter (WDM) regime and demonstrate good-to-excellent agreement with reference Kohn-Sham calculations under WDM conditions at a minuscule fraction of the computational cost of corresponding orbital-based simulations.