Bell Anthony M T, Henderson C Michael B, Wendlandt Richard F, Harrison Wendy J
Acta Crystallogr Sect E Struct Rep Online. 2009 Feb 21;65(Pt 3):i16-i17. doi: 10.1107/S1600536809005054.
The apatite-type compound, penta-strontium tris-[arsenate(V)] chloride, Sr(5)(AsO(4))(3)Cl, has been synthesized by ion exchange at high temperature from a synthetic sample of mimetite [Pb(5)(AsO(4))(3)Cl] with SrCO(3) 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 A(5)(YO(4))(3)X (A = divalent cation, Y = penta-valent cation, and X = F, Cl or Br) in the space group P6(3)/m. The structure consists of isolated tetra-hedral AsO(4) (3-) anions (the As atom and two O atoms have m symmetry), separated by two crystallographically independent Sr(2+) cations that are located on mirror planes and threefold rotation axes, respectively. One Sr atom is coordinated by nine O atoms and the other by six. The chloride anions (site symmetry ) are at the 2a sites and are located in the channels of the structure.
磷灰石型化合物五锶三[砷酸盐(V)]氯化物，即Sr₅(AsO₄)₃Cl，是通过高温离子交换法，以氯磷铅矿[Pb₅(AsO₄)₃Cl]的合成样品与SrCO₃反应制备得到的，副产物为SrCO₃。基于高分辨率同步辐射X射线粉末衍射数据的Rietveld精修结果表明，该标题化合物与其他通式为A₅(YO₄)₃X（A = 二价阳离子，Y = 五价阳离子，X = F、Cl或Br）的卤代磷灰石具有相同的结构，空间群为P6₃/m。其结构由孤立的四面体AsO₄³⁻阴离子（As原子和两个O原子具有m对称性）组成，由两个分别位于镜面和三重旋转轴上的晶体学独立的Sr²⁺阳离子分隔开。一个Sr原子由九个O原子配位，另一个由六个O原子配位。氯离子（位点对称性）位于2a位点，处于结构的通道中。
