Electronic bonding and optical properties of the H2-H2O phase at high pressure

The electronic structure and the optical properties of the cubic hydrate H2-H2O at high pressure are elucidated by means of first-principles local-density calculations. The results are compared with the Ic phase of ice. It is shown that the encapsulated H2 molecules interact weakly with the H2O network. The valence-band structure is only slightly modified while the conduction band becomes very different. A number of important physical properties including the bulk modulus, optical-absorption spectrum, refractive index, pressure dependence of the gap, etc., are predicted for H2-H2O