Bonding and Electronic Properties of Ice at High Pressure

TL;DR

This study uses ab initio simulations to explore the high-pressure phases of ice, focusing on their electronic properties, phase transitions, and orbital characteristics at megabar pressures.

Contribution

It provides detailed analysis of the metallic Cmcm phase and insulating Pnma phase of ice, including Fermi surface analysis and Wannier orbital comparison, revealing electronic structure changes under extreme pressure.

Findings

Cmcm phase exhibits Fermi nesting potential.

Pnma phase shows deformed Wannier orbitals unlike ice X.

High-pressure phases of ice have distinct electronic properties.

Abstract

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.