open access

https://hdl.handle.net/2115/52370

Lowering symmetry of filled ice Ic hydrogen hydrate under low temperatures and high pressures

日本語

2013-03-31

Institute of Low Temperature Science, Hokkaido University

Low Temperature Science

71

173-180

Low-temperature and high-pressure experiments were performed with filled ice Ic structure of hydrogen hydrate at the unexplored conditions of 5 to 55 GPa and 30 to 300 K using diamond anvil cells and a heliumrefrigeration cryostat. In-situ X-ray diffractometry revealed that the cubic filled ice Ic structure transformed to a tetragonal structure at low temperatures and high pressures and the axis ratio of the tetragonal phase changed depending on pressure and temperature. These results were consistent with theoretical predictions determined by first principle calculations. In addition, further change in the lattice parameters was observed from about 45 to 50 GPa, which suggested the existence of a transformation to another high-pressure phase above 50 GPa throughout the temperature region examined. The reason for transforming to the tetragonal structure was inferred; it might be induced due to changes in the vibrational or rotational modes of the hydrogen molecules under low temperature and high pressure.

紀要論文

Version of Record

1880-7593