Metallization of Molecular Hydrogen: Predictions from Exact-Exchange Calculations

We study metallization of molecular hydrogen under pressure using exact-exchange (EXX) Kohn-Sham density-functional theory in order to avoid well-known underestimates of band gaps associated with standard local-density or generalized-gradient approximations. Compared with the standard methods, the EXX approach leads to considerably (1–2 eV) higher gaps and significant changes in the relative energies of different structures. Metallization is predicted to occur at a density of $\gtrsim 0.6\mathrm{mol}/{\mathrm{cm}}^3$ (corresponding to a pressure of $\gtrsim 400\mathrm{GPa}$), consistent with all previous measurements.