LiCe₉Mo₁₆O₃₅

The structure of lithium nona­cerium hexa­deca­molybdenum penta­trideca­oxide, LiCe₉Mo₁₆O₃₅, is isotypic with LiNd₉Mo₁₆O₃₅ [Gougeon Gall, Cuny, Gautier, Le Polles, Delevoye & Trebosc (2011). Chem. Eur. J. 17, 13806-13813]. It is characterized by Mo₁₆O₂₆ⁱO₁₀^a units (where i = inner and a = apical) containing Mo₁₆ clusters that share some of their O atoms to form infinite molybdenum cluster chains running parallel to the b axis and separated by Li⁺ and Ce³⁺ cations. The Mo₁₆ cluster units are centred at Wyckoff positions 2c and have point-group symmetry 2/m. The Li⁺ atom, in a flattened octa­hedron of O atoms, is in a 2a Wyckoff position with 2/m symmetry. The Ce³⁺ cations have coordination numbers to the O atoms of 6, 9 or 10. Two Ce, two Mo and five O atoms lie on sites with m symmetry (Wyckoff site 4i), and one Ce and one O atom on sites with 2/m symmetry (Wyckoff sites 2b and 2d, respectively).

The pyrochlore-type molybdate Pr₂Mo_1.73Sc_0.27O₇

Dipraseodymium molybdenum scandium hepta­oxide, Pr₂Mo_1.73Sc_0.27O₇, crystallizes in the cubic pyrochlore-type structure. In the crystal, (Mo,Sc)O₆ octa­hedra are linked together by common corners, forming a three-dimensional [(Mo,Sc)₂O₆] framework. The Pr atom and another O atom atom are located in the voids of this framework. The Mo and the Sc atom are distributed statistically over the same 16d crystallographic position, with site-occupancy factors of 0.867 (3) and 0.133 (3), respectively. The Pr³⁺ ions are surrounded by six O atoms from the MoO₆ octa­hedra and by two other O atoms, forming a ditrigonal scalenohedron. All atoms lie on special positions. The Pr and the statistically distributed (Mo,Sc) sites are in the 16c and 16d positions with .-3m symmetry, and two O atoms are in 48f and 8a positions with 2.mm and -43m site symmetry, respectively.