Van-der-Waals exchange-correlation functionals and their high pressure and warm dense matter applications

TL;DR

This paper evaluates various van-der-Waals exchange-correlation functionals for modeling warm dense hydrogen, focusing on molecular properties and transition behaviors to identify the most suitable functional.

Contribution

It provides a comparative analysis of different functionals, highlighting the performance of r2SCAN and vdW functionals in modeling hydrogen's molecular to metallic transition.

Findings

r2SCAN best reproduces bond length and dissociation energy

vdW functionals and HSE06 perform similarly or worse than PBE

Differences in functionals affect ion structure and electronic properties during transition

Abstract

We investigate basic hydrogen quantities like the molecular bond length, the molecular dissociation energy and the van-der-Waals interaction in idealized situations in an effort to discern a suitable exchange-correlation functional for the molecular to metal transition in warm dense hydrogen. The best reproduction of bond length and dissociation energy is given by the r2SCAN functional, several vdW functionals and also HSE06 fair qualitatively and quantitatively no better than PBE or worse. In addition we investigate quantities like the static and dynamic ion structure factor, and the electronic DOS to determine differences between exchange-correlation functionals with and without van-der-Waals corrections in the transition region from the molecular to the metallic regime of hydrogen.