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Bonding and Electronic Properties of Ice at High Pressure

The properties of water ice at megabar pressure are characterized with ab initio computer simulations. The focus lies on the metallic Cmcm phase and its insulating distorted analogue with Pnma symmetry. Both phases were recently predicted to occur at 15.5 and 12.5 Mbar respectively [Phys. Rev. Lett. 105 (2010) 195701]. The Fermi surface of the Cmcm phase is analyzed and possibility of Fermi nesting to occur is discussed. The Wannier orbital are computed for the Pnma structure and compared to ice X. While ice X shows typical sp3 hybridization, in the Pnma structure, the orbitals are deformed and no longer all aligned with the hydrogen bonds.