Abstract

We report a quasiparticle study of the pressure-induced isostructural insulator-metal transition in solids by the mechanism of band-gap closure. Two examples are investigated: solid Xe and molecular solid hydrogen. The band gaps are calculated with a first-principles quasiparticle approach, in which the electron self-energy operator is expanded to first order in the screened Coulomb interaction, viz., the GW approximation. For the case of solid xenon, the crystal structure has been experimentally established to be hexagonal-close-packed (hcp) in the vicinity of the observed metallization pressure of 132(\ifmmode\pm\else\textpm\fi{}5) GPa. Our calculation for solid xenon yields a metallization pressure of 128 GPa, in good agreement with experiment. The theoretical results further quantitatively explain all the salient features observed in the experimental optical spectra at metallization. For molecular solid hydrogen the structure has yet to be determined definitively. Our calculations are carried out for structures in which hydrogen molecules assume an hcp arrangement. The quasiparticle results are compared with those from Hartree-Fock (HF) and local-density approximation (LDA) calculations.

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