Acta Cryst. (2007). E63, i199  [ doi:10.1107/S1600536807058588 ]

Langbeinite-related K₂FeSn(PO₄)₃ from single-crystal data

I. V. Zatovsky, M. M. Yatskin, V. N. Baumer, N. S. Slobodyanik and O. V. Shishkin

Abstract: Crystals of dipotassium iron(III) tin(IV) tris(orthophosphate) were grown from a self-flux in the system K₂O-P₂O₅-Fe₂O₃-SnO₂. The title compound is isotypic with the mineral langbeinite, K₂Mg₂(SO₄)₃. Its three-dimensional [M₂(PO₄)₃] framework is composed of [MO₆] (M = Sn, Fe) octahedra and [PO₄] tetrahedra interlinked via vertices. In comparison with the previous refinement from X-ray powder data [Aatiq, Haggouch, Bakri, Lakhdar & Saadoune. (2006). Powder Diffr. 21, 214-219], the present reinvestigation from single-crystal data allows a more precise determination of the distribution of the Fe and Sn atoms over two crystallographic positions and a revision of the P-O and M-O [M = K, (Fe, Sn)] bond lengths. For the two K⁺ cations, two different polyhedra with coordination numbers of 9 and 12 are observed. The (Fe, Sn) and K atoms are located on threefold axes.

Online 21 November 2007

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