Pressure-induced electronic and structural phase transitions in solid hydrogen

Abstract

Possible induced electronic and structural phase transitions in solid hydrogen are studied using a unified theoretical approach---the local-density total-energy full-potential linearized-augmented-plane-wave method---which has the precision to treat the highly anisotropic ${\mathrm{Pa}}_{3}$ molecular phase on the same footing as the monatomic close-packed phases. The pressure-induced metallization by band overlap and bond length relaxation within the ${\mathrm{Pa}}_{3}$ structure of molecular solid hydrogen is described and discussed; the calculations predict an insulator-to-metal phase transition at 1.7\ifmmode\pm\else\textpm\fi{}0.2 Mbar. At a much higher pressure of 4\ifmmode\pm\else\textpm\fi{}1 Mbar, a structural phase transition takes place to a monatomic metallic hcp phase with a high superconducting transition temperature.