Chlorapatite: Ca5(AsO4)3Cl

Abstract

Chlorapatite (pentacalcium triarsenate chloride), Cas-(AsO4)3C1 crystallizes in the hexagonal system and is closely related to its phosphate analogs, Ca5(PO4)3X (X = Cl, OH), but has a slightly modified structure in terms of anion sites.

Rietveld refinement of Sr5(AsO4)3Cl from high-resolution synchrotron data

“…Powder diffraction data for the Sr containing As-apatite Sr 5 (AsO 4 ) 3 Cl (Kreidler & Hummel, 1970) was indexed in space group P6 3 /m. Related crystal structures have also been reported for Ca 5 (AsO 4 ) 3 Cl (Wardojo and Hwu, 1996) Cl (Đordević et al, 2008). The crystal structure of Sr 5 (AsO 4 ) 3 Cl in space group P6 3 /m is reported in the present communication.…”

“…Atomic coordinates as starting parameters for the Rietveld (Rietveld, 1969) refinement of the present phases were taken from Bell et al (2008); Dai et al (1991); de Villiers et al (1971). For related Sr-Cl-apatites, see: Ðordević et al (2008); Sudarsanan & Young, (1974, 1980; Beck et al (2006);Noetzold et al (1995); Noetzold & Wulff (1996, 1997, 1998; Swafford & Holt (2002); Wardojo & Hwu (1996). For synthetic work, see: Baker (1966); Essington (1988); Harrison et al (2002).…”

The crystal structure of svabite, Ca5(AsO4)3F, an arsenate member of the apatite supergroup

“…White et al 2005), few data are available for the corresponding As-analogues. Single-crystal X-ray diffraction studies have been performed by Wardojo and Hwu (1996) on synthetic Ca 5 (AsO 4 ) Cl and Biagioni and Pasero (2013) on johnbaumite. The results of the X-ray single-crystal study of the three natural calcium arsenate apatites were presented by Dai and Harlow (1991) in a conference abstract, but to our knowledge the details of this work have not been published.…”

Synthesis and Neutron Diffraction Study of La5Si2BO13, an Analog of the Apatite Mineral

“…A very low distortion is also present in the vacancy bearing La Si O apatite (M1}O3 minus M1}O1 is 0.303 A > ). This e!ect is not due to the larger size of the tetrahedral polyhedron in La Si BO with respect to the PO -bearing apatites: comparison with Ca apatites with As in the tetrahedral site (11) suggests that increasing the size of the tetrahedral cation increases the distortion in the M1 polyhedron (0.43 vs 0.39 A > in Ca (AsO )Cl vs Ca (PO )Cl apatites), indicating that the lower distortion in La Si BO may be an e!ect of substitution with a trivalent cation.…”