Assessing the accuracy of hybrid exchange-correlation functionals for the density response of warm dense electrons

TL;DR

This study evaluates the accuracy of various hybrid exchange-correlation functionals in predicting the density response of warm dense electrons, comparing results to quantum Monte-Carlo data to identify the most reliable functionals under extreme conditions.

Contribution

It provides a systematic assessment of hybrid XC functionals for warm dense matter, highlighting the improved performance of certain functionals over traditional ones in this regime.

Findings

HSE03 functional performs well in describing warm dense electron response.

Hybrid functionals like PBE0 and HSE06 show improved accuracy over PBE and LDA.

B3LYP does not perform well for the studied warm dense matter systems.

Abstract

We assess the accuracy of common hybrid exchange-correlation (XC) functionals (PBE0, PBE0-1/3, HSE06, HSE03, and B3LYP) within Kohn-Sham density functional theory (KS-DFT) for the harmonically perturbed electron gas at parameters relevant for the challenging conditions of warm dense matter. Generated by laser-induced compression and heating in the laboratory, warm dense matter is a state of matter that also occurs in white dwarfs and planetary interiors. We consider both weak and strong degrees of density inhomogeneity induced by the external field at various wavenumbers. We perform an error analysis by comparing to exact quantum Monte-Carlo results. In the case of a weak perturbation, we report the static linear density response function and the static XC kernel at a metallic density for both the degenerate ground-state limit and for partial degeneracy at the electronic Fermi temperature. Overall, we observe an improvement in the density response for partial degeneracy when the PBE0, PBE0-1/3, HSE06, and HSE03 functionals are used compared to the previously reported results for the PBE, PBEsol, LDA, AM05, and SCAN functionals; B3LYP, on the other hand, does not perform well for the considered system. Together with the reduction of self-interaction errors, this seems to be the rationale behind the relative success of the HSE03 functional for the description of the experimental data on aluminum and liquid ammonia at WDM conditions.