Properties of metal hydrides under high pressure studied using synchrotron radiation X-rays

放射光を利用した金属水素化物の高圧研究

町田 晃彦

Machida, Akihiko

放射光は水素化,脱水素化に伴う構造,電子状態の研究に適している。水素と金属との結合状態又は相互作用の理解に高圧下での研究と組合せることは有効である。格子の圧縮によって高密度状態を実現したときに、水素と金属の結合状態が変化することによって引き起こされる現象の観測から相互作用に関する知見が得られる。また、高水素圧力下では、水素の反応性が増大し、新奇の水素化物合成も期待される。放射光を利用した高圧下における構造,電子状態の変化について最近の成果を紹介する。

Synchrotron radiation (SR) X-rays enable us to investigate the structural and electronic properties of metals that change often dramatically on hydrogenation and/or dehydrogenation. Metal hydrides have been investigated with a focus on hydrogen-metal bonding and hydrogen-hydrogen interaction for their densified states realized under high pressure. Application of pressure results in contraction of the metal lattice and decrease in the interatomic distances. The nature of hydrogen-metal bonding state would change significantly and becomes to be clearly detectable. Another aspect of high pressure effect is direct hydrogenation of metals. The chemical potential of hydrogen increases steeply with increasing pressure. Consequently, the hydrogen dissociation into metal is enhanced. Novel hydrides would be prepared by direct hydrogenation of metals with hydrogen-fluid chemically actived at high temperature and high pressure.