NdHO, a novel oxyhydride

A new metal oxyhydride; neodymium oxyhydride, NdHO, has been synthesized from a reactant mixture of metal hydride (CaH2 or NdH3) and neodymium oxide (Nd2O3). The unit cell dimensions decrease smoothly in the series from LaHO, CeHO, PrHO to NdHO, in line with the lanthanide contraction. The crystal structure of NdHO is described on the basis of Rietveld refinement on neutron powder diffraction data: Space group: P4/nmm (no. 129, D4h7). Axis lengths: a=7.8480(5) A, c=5.5601(8) A. Volume: V=342.46(6) A3. The tetragonal structure is derived from the fluorite structure, showing complete ordering of hydride and oxide ions over the anion sublatttice. The formation of NdHO was further substantiated by Raman spectroscopy. - Graphical Abstract: View of the NdHO structure. Highlights: → CaH2 or NdH3 react with Nd2O3 in reducing atmospheres forming a new oxyhydride, NdHO. → NdHO crystalises in tetragonal space group P4/nmm with axes a=b=7.8480(5) A and c=5.5601(8) A. → The structure is similar to the fluorite structure with complete ordering of hydride and oxide ions. → Unit cell dimensions decrease smoothly in the series from LaHO, CeHO, PrHO to NdHO. → The formation of NdHO is substantiated by Raman spectroscopy.