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Novel Hydrogen Clathrate Hydrate

2020; American Physical Society; Volume: 125; Issue: 25 Linguagem: Inglês

10.1103/physrevlett.125.255702

1092-0145

Yu Wang, Konstantin Glazyrin, Valery V. Roizen, Artem R. Oganov, Ivan Yu. Chernyshov, Xiao Zhang, Eran Greenberg, Vitali B. Prakapenka, Xue Yang, Shuqing Jiang, Alexander F. Goncharov,

Inorganic Fluorides and Related Compounds

We report a new hydrogen clathrate hydrate synthesized at 1.2 GPa and 298 K documented by single-crystal X-ray diffraction, Raman spectroscopy, and first-principles calculations. The oxygen sublattice of the new clathrate hydrate matches that of ice II, while hydrogen molecules are in the ring cavities, which results in the trigonal R3c or R-3c space group (proton ordered or disordered, respectively) and the composition of (H2O)6H2. Raman spectroscopy and theoretical calculations reveal a hydrogen disordered nature of the new phase C1', distinct from the well-known ordered C1 clathrate, to which this new structure transforms upon compression and/or cooling. This new clathrate phase can be viewed as a realization of a disordered ice II, unobserved before, in contrast to all other ordered ice structures.