Nonstoichiometric molybdenum hydride

The molybdenum-hydrogen system was studied in a diamond anvil cell at high hydrogen pressure up to 30 GPa at room temperature by X-ray diffraction. At pressure around 4 GPa a phase transformation was observed of a bcc metal to a hydride with a hcp metal lattice and H/Mo ≈ 1.1. Further hydrogen pressure increase resulted in a continuous increase of the hydrogen content of the hydride. At about 15 GPa the hydrogen content reached saturation, and no further hydrogen absorption occured up to the maximal reached pressure. The saturation composition H/Mo = 1.35 (10) was estimated from volumetric considerations. •Synthesis of molybdenum hydride from elements was performed at high pressure in a diamond anvil cell.•The pressures of formation and decomposition were determined.•The hydrogen content of the hydride was estimated from the volume consideration.