The crystal structure of cubic C-type samarium sesquioxide, Sm2O3

Cubic C-type samarium sesquioxide, Sm2O3, was prepared by thermal decomposition of samarium carbonate. Its crystal structure was refined based on neutron powder diffraction data [space group Ia (3) over bar, a = 1092.77(6) pm] in order to accurately determine the oxygen atom positions. Isotopically enriched (Sm2O3)-Sm-154 was used for the neutron diffraction work because of the enormous absorption cross section of the natural isotopic mixtures for thermal neutrons. Crystal structure refinements by the Rietveld technique confirm the cubic bixbyite type and yield structure data of high accuracy. Interatomic distances between Sm1 (Wyckoff site 8a) and oxygen are 6 x 235.0(2) pm, and between Sm2 (Wyckoff site 24d) and oxygen 2 x 231.6(2) pm, 2 x 233.7(2) pm, 2 x 240.2(2) pm with a weighted average of (d) over bar (Sm-O) = 235.1(2) pm.