Rietveld refinement of Ba(5)(AsO(4))(3)Cl from high-resolution synchrotron data.

The apatite-type compound Ba(5)(AsO(4))(3)Cl, penta-barium tris-[arsenate(V)] chloride, has been synthesized by ion exchange at high temperature from a synthetic sample of mimetite (Pb(5)(AsO(4))(3)Cl) with BaCO(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, X = Cl, Br) in space group P6(3)/m. The structure consists of isolated tetra-hedral AsO(4) (3-) anions (m symmetry), separated by two crystallographically independent Ba(2+) 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.

Related literature

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 ▶).

Experimental

Crystal data

As3Ba5ClO12

M = 1138.85

Hexagonal,

a = 10.5570 (1) Å

c = 7.73912 (8) Å

V = 746.98 (1) Å3

Z = 2

Synchrotron radiation

λ = 0.998043 Å

μ = 56.07 (1) mm−1

T = 298 K

Specimen shape: cylinder

40 × 0.7 × 0.7 mm

Specimen prepared at 100 kPa

Specimen prepared at 1258 K

Particle morphology: powder, white

Data collection

In-house design diffractometer

Specimen mounting: capillary

Specimen mounted in transmission mode

Scan method: step

Absorption correction: none

2θmin = 2, 2θmax = 70°

Increment in 2θ = 0.01°

Refinement

R p = 0.059

R wp = 0.082

R exp = 0.067

R B = 0.090

S = 1.23

Excluded region(s): 2-6 degrees 2θ.

Profile function: Fundamental Parameters

464 Bragg reflections

21 parameters

Preferred orientation correction: none

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 ▶).

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808026901/wm2188sup1.cif

Rietveld powder data: contains datablocks I. DOI: 10.1107/S1600536808026901/wm2188Isup2.rtv

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

As3Ba5Cl1O12	Z = 2
Mr = 1138.85	Dx = 5.063 (1) Mg m−3
Hexagonal, P63/m	Synchrotron radiation λ = 0.998043 Å
a = 10.5570 (1) Å	µ = 56.07 (1) mm−1
b = 10.5570 (1) Å	T = 298 K
c = 7.73912 (8) Å	Specimen shape: cylinder
α = 90º	40 × 0.7 × 0.7 mm
β = 90º	Specimen prepared at 100 kPa
γ = 120º	Specimen prepared at 1258 K
V = 746.98 (1) Å3	Particle morphology: powder, white

In-house design diffractometer	T = 298 K
Monochromator: Si(111) channel-cut crystal	2θmin = 2, 2θmax = 70º
Specimen mounting: capillary	Increment in 2θ = 0.01º
Specimen mounted in transmission mode	Increment in 2θ = 0.01º
Scan method: step

Rp = 0.059	Profile function: Fundamental Parameters
Rwp = 0.082	21 parameters
Rexp = 0.067	3 constraints
RB = 0.090	?
S = 1.23	(Δ/σ)max = 0.001
Wavelength of incident radiation: 0.998043 Å	Preferred orientation correction: None
Excluded region(s): 2-6 degrees 2θ.

	x	y	z	Uiso*/Ueq
Ba1	0.3333	0.6667	0.0061 (9)	0.059 (1)
Ba2	0.2445 (4)	0.9874 (6)	0.2500	0.065 (1)
As1	0.4047 (7)	0.3716 (7)	0.2500	0.059 (2)
O1	0.347 (7)	0.495 (6)	0.2500	0.13 (2)
O2	0.591 (4)	0.473 (4)	0.2500	0.08 (1)
O3	0.354 (2)	0.280 (3)	0.068 (3)	0.065 (8)
Cl1	0.0000	0.0000	0.0000	0.070 (6)

Ba1—O1i	2.67 (5)	Ba2—O3vi	2.62 (4)
Ba1—O1ii	2.67 (5)	Ba2—O3vii	3.05 (4)
Ba1—O1	2.67 (5)	Ba2—O3viii	3.05 (4)
Ba1—O2iii	2.81 (4)	Ba2—O1ii	3.14 (4)
Ba1—O2iv	2.81 (4)	Ba2—Cl1viii	3.281 (5)
Ba1—O2v	2.81 (4)	Ba2—Cl1ix	3.281 (5)
Ba1—O3iv	3.12 (3)	As1—O3	1.64 (2)
Ba1—O3iii	3.12 (3)	As1—O3x	1.64 (2)
Ba1—O3v	3.12 (3)	As1—O1	1.70 (8)
Ba2—O2i	2.59 (4)	As1—O2	1.70 (4)
Ba2—O3iv	2.62 (4)
O3—As1—O3x	118 (2)	O3—As1—O2	108 (2)
O3—As1—O1	108 (1)	O3x—As1—O2	108 (2)
O3x—As1—O1	108 (1)	O1—As1—O2	106 (2)

Ba1—O1	2.67 (5)
Ba1—O2i	2.81 (4)
Ba1—O3i	3.12 (3)
Ba2—O2ii	2.59 (4)
Ba2—O3iii	2.62 (4)
Ba2—O3iv	3.05 (4)
Ba2—O1v	3.14 (4)
Ba2—Cl1iv	3.281 (5)
As1—O3	1.64 (2)
As1—O1	1.70 (8)
As1—O2	1.70 (4)

O3—As1—O3vi	118 (2)
O3—As1—O1	108 (1)
O3—As1—O2	108 (2)
O1—As1—O2	106 (2)

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) ; (vi) .