Reinvestigation of Crystal Structure and Non‐Stoichiometry in Copper Hydride, CuH1–x (0 ≤ x ≤ 0.26)

Abstract

AbstractCopper hydride and deuteride were reinvestigated by X‐ray and neutron powder diffraction, revealing a pronounced phase width with respect to the hydrogen (deuterium) content. Synthesis from aqueous copper(II) sulfate with hypophosphoric acid solutions yields samples with a broad distribution of compositions and variations of up to 6.5 % in unit cell volume. The result is a metrical distortion with (hkl) dependent asymmetry and broadening of powder diffraction reflections. Patterns of such samples were described using a model with five copper hydride (deuteride) phases with different lattice parameters. A method for developing and refining reasonable multiphase models despite high correlation of parameters is described. Simultaneous refinement on X‐ray and neutron powder diffraction on a deuteride sample suggests a statistical occupation of deuterium on less than half of the tetrahedral voids of a hexagonal close packing of copper atoms [P63/mmc, a = 2.9024(5) Å, c = 4.632(2) Å, Cu in 2c, D in 4f with z = 0.6497(8), deuterium occupation 0.368(6)]. The reaction of aqueous copper(II) chloride with sodium boronate solutions yields copper hydride with a stoichiometric composition [P63/mmc, a = 2.8777(3) Å, c = 4.570(1) Å, Cu in 2c, H in 4f with z = 0.640(1), hydrogen occupation 1/2]. The structures are isotypic to ScD0.33 and reveal a surprising analogy to lanthanide hydrides.