A synchrotron X-ray study of the electron density in C-type rare earth oxides

Structure factors for small synthetic crystals of the C-type rare earth (RE) sesquioxides Y₂O₃, Dy₂O₃ and Ho₂O₃ were measured with focused λ = 0.7000 (2) Å, synchrotron X-radiation, and for Ho₂O₃ were re-measured with an MoKα (λ = 0.71073 Å) source. Approximate symmetry in the deformation electron density (Δρ) around a RE atom with pseudo-octahedral O coordination matches the cation geometry. Interactions between heavy metal atoms have a pronounced effect on the Δρ map. The electron-density symmetry around a second RE atom is also perturbed significantly by cation–anion interactions. The compounds magnetic properties reflect this complexity. Space group Ia, cubic, Z = 16, T = 293 K: Y₂O₃, M_r = 225.82, a = 10.5981 (7) Å, V = 1190.4 (2) ų, D_x = 5.040 Mg m⁻³, μ_0.7 = 37.01 mm⁻¹, F(000) = 1632, R = 0.067, wR = 0.067, S = 9.0 (2) for 1098 unique reflections; Dy₂O₃, M_r = 373.00, a = 10.6706 (7) Å, V = 1215.0 (2) ų, D_x = 8.156 Mg m⁻³, μ_0.7 = 44.84 mm⁻¹, F(000) = 2496, R = 0.056, wR = 0.051, S = 7.5 (2) for 1113 unique reflections; Ho₂O₃, M_r = 377.86, a = 10.606 (2) Å, V = 1193.0 (7) ų, D_x = 8.415 Mg m⁻³, μ_0.7 = 48.51 mm⁻¹ F(000) = 2528, R = 0.072, wR = 0.045, S = 9.2 (2) for 1098 unique reflections of the synchrotron data set.

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