In situ diffraction study of the formation of rhenium hydride at high pressure

The formation of rhenium hydride from rhenium and hydrogen at high pressure has been studied using a diamond anvil cell and in-situ X-ray diffraction. Rhenium hydride forms by 5.3 GPa at room temperature. The hydride has an hcp structure with interstitial hydrogen. By 8.6 GPa, the stoichiometry of rhenium hydride saturates to ReH_0.38±0.04, a value significantly greater than found in earlier studies of quenched material. After saturation at 8.6 GPa, the interstitial hydrogen is “incompressible,” such that the difference in the volumes between rhenium metal and rhenium hydride remains nearly constant up to at least 20 GPa.