Fig. 1: DFT benchmarking for the metallization pressure of hcp 4He.
From: Excitonic insulator to superconductor phase transition in ultra-compressed helium
a Electronic band gap, Eg, expressed as a function of pressure and calculated with different DFT functionals. Negative Eg values indicate overlapping between the VBM and CBM levels. The grey region indicates the stability range of metallic helium as calculated with QMC methods7. b Electronic localization function (ELF isosurface = 0.8, yellow) of solid helium at 12 and 36 TPa in a red-green-blue color scale with red denoting high electronic density and blue low electronic density. c Lowest conduction (red) and highest valence (blue) bands expressed as a function of reciprocal wave vector in the kz = 0 plane; the grey and transparent plane represents the Fermi surface.
