Received 30 July 2008
aSynchrotron Radiation Source, STFC Daresbury Laboratory, Daresbury, Warrington, Cheshire, WA4 4AD, England,bSchool of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, M13 9PL, England, and cDepartment of Geology and Geological Engineering, Colorado School of Mines, Golden, CO 80401, USA
Correspondence e-mail: firstname.lastname@example.org
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 AsO43- 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.
For crystal chemistry of apatites, see: Mercier et al. (2005); White & ZhiLi (2003); Wu et al. (2003). For powder diffraction data on Ba-containing As-apatites, see: Kreidler & Hummel (1970); Dunn & Rouse (1978). Atomic coordinates as starting parameters for the Rietveld (Rietveld, 1969) refinement of the present phases were taken from Chengjun et al. (2005); Dai et al. (1991); de Villiers et al. (1971). For related Ba-Cl-apatites, see: Đordevic et al. (2008); Hata et al. (1979); Reinen et al.(1986); Roh & Hong (2005); Schiff-Francois et al. (1979). For synthetic work, see: Baker (1966); Essington (1988); Harrison et al. (2002).
Data collection: local software; cell refinement: CELREF (Laugier & Bochu, 2003); data reduction: local software; method used to solve structure: coordinates taken from a related compound; program(s) used to refine structure: TOPAS (Coelho, 2000); molecular graphics: Balls and Sticks (Kang & Ozawa, 2003); software used to prepare material for publication: publCIF (Westrip, 2008).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WM2188 ).
AMTB acknowledges the use of the EPSRC's Chemical Database Service at Daresbury (Fletcher et al., 1996). AMTB also acknowledges the referees and Co-editor whose suggestions and comments helped to improve this paper.
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