Compressibility of hydrogen in Ni and Re hosts at pressures to 123 GPa

Abstract

Ni-H and Re-H binary systems have been studied at room temperature by X-ray diffraction in a diamond-anvil cell. The formation of the hydrides NiH and ReHo.4 with no change in the types of the host metal lattices was observed through the expansion of the host lattices. No structure changes were observed in the metal sub-lattice of either hydride under increasing pressure and the equations of state have been obtained to 123GPa. The difference in the partial hydrogen volume as a function of pressure between the Ni-H and Re-H systems can be understood with reference to the behaviour of conduction electrons. The pressure dependence of the partial hydrogen volume in these hydrides supports the hypothesis of the apparent common-volume behaviour of hydrogen in a metallic environment.

Key Words:

• Metal hydrides
• High pressure
• Diamond- anvil cell
• Equation of state