Accurate Density Functional Theory Simulations Across the Warm-Dense-Matter Regime: Thermal Meta-GGA Exchange Correlation and Nuclear Quantum Effects

First-principles methods based on orbital-dependent and orbital-free density functional theory take into account the electron quantum effects and provide a compromise between reliability and computational efficiency for simulations of matter across extreme conditions of pressure and temperature in the warm-dense matter (WDM) regime. With that, the standard molecular dynamics approach treats ions classically within the Born--Oppenheimer approximation, omitting nuclear quantum effects (NQE’s). The NQE’s at high pressure are not negligible in a wide range of temperatures and must be taken into account for accurate predictions. In this talk we will discuss recent progress in the development of meta-generalized gradient approximation (meta-GGA) exchange- correlation functional enhanced by the GGA-level thermal corrections providing improved accuracy across the temperature regimes. Together with quantum treatment of ions via path integral molecular dynamics, our approach provides a systematically improved accuracy of WDM simulations, as we show in an example of dense hydrogen and deuterium plasmas.