Received 9 August 2013
In the crystal structure of Y4F2[Si2O7][SiO4], three fundamental building blocks are present, viz. anionic disilicate and orthosilicate units ([Si2O7]6- and [SiO4]4-) and cationic [F2Y4]10+ entities. The latter are built up by two [FY3]8+ triangles sharing a common edge. The four crystallographically independent Y3+ cations display coordination numbers of eight for one and of seven for the other three cations, provided by oxide and fluoride anions. The overall arrangement of the building blocks can be considered as layer-like parallel to the ac plane.
For isotypic Er4F2[Si2O7][SiO4], see: Müller-Bunz & Schleid (2001). For the minor by-product phase Y3F[Si3O10], see: Müller-Bunz & Schleid (1998). For the crystal structure of allanite (old name orthite), see: Rumanova & Nikoleva (1959).
Data collection: COLLECT (Nonius, 1998); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: SCALEPACK and DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: SHELXL97.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WM2768 ).
This work was supported by the State of Baden-Württemberg (Stuttgart) and the Deutsche Forschungsgemeinschaft (DFG, Frankfurt/Main) within the funding program Open Access Publishing.
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