Weil Matthias, Stöger Berthold, Aleksandrov Lyubomir
Acta Crystallogr Sect E Struct Rep Online. 2009 May 23;65(Pt 6):i45. doi: 10.1107/S1600536809018108.
The title compound, dineodymium(III) tris-[tungstate(VI)], is a member of the Eu(2)(WO(4))(3) structure family and crystallizes isotypically with other rare earth tungstates and molybdates of this formula type. The structure is a derivative of the scheelite (CaWO(4)) structure and can be considered as an ordered defect variant with a threefold scheelite supercell and one rare earth (RE) site unoccupied. The Nd(3+) cations are coordinated by eight O atoms in form of a distorted bicapped trigonal prism. The two unique W cations are tetra-hedrally surrounded by O atoms. One WO(4) tetra-hedron has 2 symmetry and is relatively undistorted whereas the other tetra-hedron differs considerably from an ideal geometry. This is caused by an additional remote O atom at a distance of 2.149 (4) Å. The resulting WO(4 + 1) polyhedra form W(2)O(8) dimers through edge-sharing. Together with the WO(4) and NdO(8) units, the three-dimensional set-up is accomplished.
标题化合物三[钨酸(VI)]二钕(III)是Eu₂(WO₄)₃结构族的一员，与该化学式类型的其他稀土钨酸盐和钼酸盐同晶型结晶。该结构是白钨矿(CaWO₄)结构的衍生物，可被视为具有三倍白钨矿超晶胞且一个稀土(RE)位点未被占据的有序缺陷变体。Nd³⁺阳离子以扭曲的双帽三棱柱形式由八个O原子配位。两个独特的W阳离子被O原子四面体包围。一个WO₄四面体具有2次对称性且相对未变形，而另一个四面体与理想几何形状有很大差异。这是由一个距离为2.149 (4) Å的额外远程O原子引起的。由此产生的WO₄₊₁多面体通过边共享形成W₂O₈二聚体。与WO₄和NdO₈单元一起，完成了三维结构。
