Computational Chemistry-Guided Syntheses and Crystal Structures of the Heavier Lanthanide Hydride Oxides DyHO, ErHO, and LuHO

Heteroanionic hydrides offer great possibilities in the design of functional materials. For ternary rare earth hydride oxide REHO, several modifications were reported with indications for a significant phase width with respect to H and O of the cubic representatives. We obtained DyHO and ErHO as well as the thus far elusive LuHO from solid-state reactions of RE2O3 and REH3 or LuH3 with CaO and investigated their crystal structures by neutron and X-ray powder diffraction. While DyHO, ErHO, and LuHO adopted the cubic anion-ordered half-Heusler LiAlSi structure type (F (4) over bar 3m, a(DyHO) = 5.30945(10) angstrom, a(ErHO) = 5.24615(7) angstrom, a(LuHO) = 5.171591(13) angstrom), LuHO additionally formed the orthorhombic anti-LiMgN structure type (Pnma; LuHO: a = 7.3493(7) angstrom, b = 3.6747(4) angstrom, c = 5.1985(3) angstrom; LuDO: a = 7.3116(16) angstrom, b = 3.6492(8) angstrom, c = 5.2021(7) angstrom). A comparison of the cubic compounds' lattice parameters enabled a significant distinction between REHO and REH1+2xO1-x (x < 0 or x > 0). Furthermore, a computational chemistry study revealed the formation of REHO compounds of the smallest rare earth elements to be disfavored in comparison to the sesquioxides, which is why they may only be obtained by mild synthesis conditions.

Automated summary

Heteroanionic hydrides show great potential in functional materials design. By employing solid-state reactions, the cubic rare earth hydride oxides DyHO, ErHO, and LuHO were synthesized, each exhibiting unique crystal structures. Computational chemistry studies suggest that the formation of REHO compounds for smaller rare earth elements is less favorable compared to sesquioxides, requiring mild synthesis conditions for their synthesis.