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

Machida, Akihiko

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.