New phase in the water-hydrogen system

A new hydrogen hydrate denoted C(0) is discovered in the H(2)O-H(2) system at -20 degrees C and hydrogen pressures near 5 kbar. Powder samples of the hydrate were quenched under high pressure to the liquid N(2) temperature and recovered to ambient pressure. Hot extraction in vacuum demonstrated that the hydrogen release from the quenched samples started immediately on heating above 77 K and completed at about 170 K. The total amount of the released hydrogen reached a molecular ratio of H(2)/H(2)O approximate to 0.13. An X-ray diffraction investigation at 80 K showed that the samples were single-phase and had a trigonal structure with a = 6.33 angstrom and c = 6.20 angstrom on hexagonal axes. (C) 2011 Elsevier B.V. All rights reserved.