Pressure Induced Metallization in the ε Phase of Solid Oxygen by ab initio Pseudopotential Plane-Wave Calculations

We perform an ab initio study on the electronic structure and charge density of the ε-oxygen under high pressure, which is obtained by powder x-ray diffraction experiment recently. Our results show that the hybridization among the σ_g*, π_u and π_g* bands in the ε-oxygen are not significant even at megabar pressure. Pressure-induced metallization occurs due to the band overlapping near the Fermi level at about 50GPa. A new network along the b-axis is formed and the O₈ characteristic in the ε phase disappears above 50GPa even though the symmetry remains unchanged.