On the effects of high temperature and high pressure on the hydrogen solubility in rhenium

In situ x-ray diffraction experiments on rhenium hydride compressed up to 46 GPa reveal a hydrogen solubility (x) significantly larger than the previously assumed saturation limit of x ~ 0.38(4). In the layered anti-CdI(2)-type structure of rhenium hydride, the hydrogen solubility was found to increase to x ~ 0.5 at 15 GPa over time. When heated to temperatures above 420 K at pressures above 23 GPa, rhenium hydride undergoes an isomorphous phase transition into the NiAs-type structure accompanied by an increase in hydrogen solubility to x ~ 0.85. The formation of fully stoichiometric rhenium hydride is discussed.