H4O and other hydrogen-oxygen compounds at giant-planet core pressures

TL;DR

This paper explores the high-pressure crystal structures of water, hydrogen, and their compounds relevant to giant-planet interiors, revealing new stable phases and compositions at extreme pressures.

Contribution

It introduces novel high-pressure structures of water and hydrogen-oxygen compounds, expanding understanding of planetary interior compositions.

Findings

Hydrogen is incorporated into ice to form H4O at pressures above 14 Mbar.

Two new stable structures of water ice, P2_1/m and I4/mmm, are predicted.

Novel phases could influence models of giant planet interiors.

Abstract

Water and hydrogen at high pressure make up a substantial fraction of the interiors of giant planets. Using ab initio random structure search methods we investigate the ground-state crystal structures of water, hydrogen, and hydrogen-oxygen compounds. We find that, at pressures beyond 14 Mbar, excess hydrogen is incorporated into the ice phase to form a novel structure with H4O stoichiometry. We also predict two new ground state structures, P2_1/m and I4/mmm, for post-C2/m water ice.