Hydrogen-Stuffed, Quartz-like Water Ice

Through use of in situ Raman spectroscopy and single-crystal/powder X-ray diffraction, we resolve the “C 0 ” phase structure discovered recently in the H 2 + H 2 O system. This phase forms at ∼400 MPa and 280 K with the nominal composition (H 2 O) 2 H 2 and three formula units per unit cell. The hexagonal structure is chiral, consisting of interpenetrating spiral chains of hydrogen-bonded water molecules and rotationally disordered H 2 molecules, and shows topological similarities with the mineral quartz. Like other clathrate hydrates and forms of ice, the protons of H 2 O molecules within C 0 are disordered. The large zeolite-like channels accommodate significant amounts of hydrogen (5.3% by weight) in a unique hydrogen-bonded lattice, which might be applicable to the thermodynamic conditions found on icy planetary bodies.