Hydrogen in polar intermetallics: Syntheses and structures of the ternary Ca5Bi3D0.93, Yb5Bi3Hx, and Sm5Bi3H∼1 by powder neutron or single crystal X-ray diffraction

The syntheses of the title compounds are described in detail. Structural characterizations from refinements of single crystal X-ray diffraction data for Yb5Bi3Hx and Sm5Bi3H∼1 and of powder neutron diffraction data for Ca5Bi3D0.93(3) are reported. These confirm that all three crystallize with the heavy atom structure type of β-Yb5Sb3, and the third gives the first proof that the deuterium lies in the center of nominal calcium tetrahedra, isostructural with the Ca5Sb3F-type structure. These Ca and Yb phases are particularly stable with respect to dissociation to Mn5Si3-type product plus H2. Some contradictions in the literature regarding Yb5Sb3 and Yb5Sb3Hx phases are considered in terms of adventitious hydrogen impurities that are generated during reactions in fused silica containers at elevated temperatures.

The structure of Ca5Bi3H0.93 occurs in the novel Ca5Sb3F structure type with D centered in the shaded calcium tetrahedra.Figure optionsDownload as PowerPoint slide