Benchmarking Exchange-Correlation Functionals in the Spin-Polarized Inhomogeneous Electron Gas under Warm Dense Conditions

TL;DR

This paper evaluates the accuracy of common exchange-correlation functionals in modeling spin-polarized inhomogeneous electron gases under warm dense conditions using quantum Monte Carlo methods, highlighting their limitations and suggesting future improvements.

Contribution

It extends previous work by assessing XC functionals in spin-polarized warm dense matter, providing practical applicability guidelines and pointing towards more accurate future functionals.

Findings

Accuracy decreases with lower density and higher wave numbers

Current XC functionals are less reliable under strong correlation conditions

Recommendations for functional applicability in warm dense matter

Abstract

Warm dense matter is a highly active research area both at the frontier and interface of material science and plasma physics. We assess the performance of commonly used exchange-correlation (XC) approximation (LDA, PBE, PBEsol, and AM05) in the spin-polarized inhomogeneous electron gas under warm dense conditions based on exact path-integral quantum Monte-Carlo calculations. This extends our recent analysis on the relevance of inhomogeneities in the spin-unpolarized warm dense electron gas [Z.~Moldabekov et al., J. Chem. Phys. 155, 124116 (2021)]. We demonstrate that the predictive accuracy of these XC functionals deteriorates with (1) a decrease in density (corresponding to an increase in the inter-electronic correlation strength) and (2) an increase of the characteristic wave number of the density perturbation. We provide recommendations for the applicability of the considered XC functionals at conditions typical for warm dense matter. Furthermore, we hint at future possibilities for constructing more accurate XC functionals under these conditions.