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Filled ice Ic 水素ハイドレートの低温高圧下における相変化

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Title: Filled ice Ic 水素ハイドレートの低温高圧下における相変化
Other Titles: Lowering symmetry of filled ice Ic hydrogen hydrate under low temperatures and high pressures
Authors: 平井, 寿子1 Browse this author →KAKEN DB
香川, 慎伍2 Browse this author
田中, 岳彦3 Browse this author
松岡, 岳洋4 Browse this author
八木, 健彦5 Browse this author →KAKEN DB
大石, 泰生6 Browse this author →KAKEN DB
山本, 佳孝7 Browse this author →KAKEN DB
大竹, 道香8 Browse this author
Authors(alt): Hirai, Hisako1
Kagawa, Shingo2
Tanaka, Takehiko3
Matsuoka, Takahiro4
Yagi, Takehiko5
Ohishi, Yasuo6
Yamamoto, Yoshitaka7
Ohtake, Michika8
Issue Date: 31-Mar-2013
Publisher: 北海道大学低温科学研究所
Journal Title: 低温科学
Journal Title(alt): Low Temperature Science
Volume: 71
Start Page: 173
End Page: 180
Abstract: 水素ハイドレート高圧相(filled ice Ic構造)についてダイヤモンドアンビルセルとヘリウム冷凍クライオスタットを用いて低温高圧実験を行った. 温度圧力条件は5から55GPaおよび30から300Kである. X線回折によって低温高圧下でfilled ice Ic構造はcubicからtetragonalに相変化し, 両相の存在領域が推定された. また, このtetragonal構造の軸比は温度圧力に依存して変化することも観察された. これらの結果は第一原理計算によって予測された結果を実験的に検証するものである. Tetragonal構造形成の誘因はゲスト水素分子の回転モードが無秩序から変化したことによると推測された. さらに, 50GPa以上では温度に依存せず別の高圧相の存在が示された.
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.
Type: bulletin (article)
Appears in Collections:低温科学 = Low Temperature Science > 第71巻

Submitter: 低温科学研究所図書室

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