Acta Cryst. (2008). E64, i63-i64  [ doi:10.1107/S1600536808026901 ]

Rietveld refinement of Ba₅(AsO₄)₃Cl from high-resolution synchrotron data

A. M. T. Bell, C. M. B. Henderson, R. F. Wendlandt and W. J. Harrison

Abstract: The apatite-type compound Ba₅(AsO₄)₃Cl, pentabarium tris[arsenate(V)] chloride, has been synthesized by ion exchange at high temperature from a synthetic sample of mimetite (Pb₅(AsO₄)₃Cl) with BaCO₃ as a by-product. The results of the Rietveld refinement, based on high resolution synchrotron X-ray powder diffraction data, show that the title compound crystallizes in the same structure as other halogenoapatites with general formula A₅(YO₄)₃X (A = divalent cation, Y = pentavalent cation, X = Cl, Br) in space group P6₃/m. The structure consists of isolated tetrahedral AsO₄^3- anions (m symmetry), separated by two crystallographically independent Ba²⁺ cations that are located on mirror planes and threefold rotation axes, respectively. The Cl^- anions are at the 2b sites ( symmetry) and are located in the channels of the structure.

Online 23 August 2008

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