Acta Crystallographica Section B

Structural Science

Volume 63, Part 6 (December 2007)

research papers

 

Reticular merohedral twinning within the La₉Sb₅O₅ structure family: structure of Pr₉Sb₅O₅, Sm₉Sb₅O₅ and Dy₉Sb₅O₅

J. Nuss and M. Jansen

Abstract: The novel antimonide oxides Pr₉Sb₅O₅, Sm₉Sb₅O₅ and Dy₉Sb₅O₅ were synthesized from the respective RESb, the rare-earth metals (RE = Pr, Sm, Dy), and RE₂O₃ (RE = Sm, Dy) or Pr₄O₇, respectively, in sealed tantalum ampoules at 1920 K. Those compounds, which are sensitive against air and moisture, form black cube-like crystals with metallic lustre. They crystallize in the La₉Sb₅O₅ type of structure, which represents a fivefold superstructure of the KCoO₂ structure: O₁₀K₅Co₅ La₉Sb₅O₅. The investigated crystals of the Sm and Dy compounds were twinned using the reticular merohedral law, with the twin symmetry 4/mm'm', and the (310) and (120) mirror planes as twinning symmetry elements. The twin index is [j] = 5.

Keywords: reticular merohedal twinning; single-crystal X-ray diffraction; rare-earth metals; antimonide oxides.

	Structure factor file (CIF format) (96.4 kbytes) [ doi:10.1107/S0108768107051282/bp5006pr9Sb5o5sup2.hkl ] Contains datablock nus147nm
	Structure factor file (CIF format) (182.7 kbytes) [ doi:10.1107/S0108768107051282/bp5006dy9sb5o5sup3.hkl ] Contains datablock twin
	Structure factor file (CIF format) (201.8 kbytes) [ doi:10.1107/S0108768107051282/bp5006sm9sb5o5sup4.hkl ] Contains datablock twin

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