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Description
The locations and occupancies of deuterium atoms in molybdenum deuteride were studied using time-of-flight neutron powder diffraction under pressures up to ∼ 6.2 GPa. The sample was synthesised in situ by reacting molybdenum powder with deuterium gas, introduced via an offline high-pressure gas-loading technique, and compressed using a Paris–Edinburgh press. Above ~4 GPa, diffraction data revealed the formation of a hexagonal deuteride phase. We confirmed the P63/mmc symmetry and determined the over-stoichiometric deuterium content to give a composition of MoD1.15, showing that our data are highly sensitive to deuterium positions and occupancies. The refined atomic positions and interatomic distances provide insight into D–Mo interactions and the origin of non-stoichiometry.