Acta Cryst. (2007). E63, i180-i181  [ doi:10.1107/S1600536807044765 ]

The whitlockite-related phosphate Ca₉Cr(PO₄)₇

I. V. Zatovsky, N. Y. Strutynska, V. N. Baumer, O. V. Shishkin and N. S. Slobodyanik

Abstract: Nonacalcium chromium(III) heptakis(orthophosphate) has been obtained from a melt in the system Cs₂O-CaO-Cr₂O₃ using a polyphosphate flux. The three-dimensional framework is related to the whitlockite structure [-Ca₃(PO₄)₃] and is built up from CaO₈ and CaO₉ polyhedra sharing vertices, edges and faces, further connected by PO₄ tetrahedra and CrO₆ octahedra. The Cr, one P and one O atom are located on threefold rotation axes. Ca₉Cr(PO₄)₇ is isotypic with Ca₉Fe(PO₄)₇. The crystal studied was an inversion twin.

Online 21 September 2007

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