Accuracy of Kohn-Sham density functional theory for warm- and hot-dense matter equation of state

TL;DR

This study evaluates the accuracy of Kohn-Sham density functional theory in modeling warm- and hot-dense matter, showing it aligns well with benchmark data and is robust across different functionals.

Contribution

It demonstrates that DFT provides accurate and consistent equations of state for WDM and HDM, validated against path integral Monte Carlo benchmarks.

Findings

DFT results agree well with PIMC benchmarks

DFT has smaller error bars and smoother data

Results are insensitive to the choice of exchange-correlation functional

Abstract

We study the accuracy of Kohn-Sham density functional theory (DFT) for warm- and hot-dense matter (WDM and HDM). Specifically, considering a wide range of systems, we perform accurate ab initio molecular dynamics simulations with temperature-independent local/semilocal density functionals to determine the equations of state at compression ratios of 3x--7x and temperatures near 1 MK. We find very good agreement with path integral Monte Carlo benchmarks, while having significantly smaller error bars and smoother data, demonstrating the accuracy of DFT for the study of WDM and HDM at such conditions. In addition, using a $\Delta$-machine learned force field scheme, we confirm that the DFT results are insensitive to the choice of exchange-correlation functional, whether local, semilocal, or nonlocal.