Rietveld refinement of AgCa10(PO4)7 from X-ray powder data.

Polycrystalline silver(I) deca-calcium heptakis(orthophos-phate), AgCa10(PO4)7, was obtained by solid-state reaction. It is isotopic with members of the series MCa10(PO4)7 (M = Li, Na, K and Cs), and is closely related to the structure of β-Ca3(PO4)2. The crystal structure of the title compound is built up from a framework of [CaO9] and two [CaO8] polyhedra, one [CaO6] octa-hedron (site symmetry 3.) and three PO4 tetra-hedra (one with site symmetry 3.). The Ag(+) cation is likewise located on a threefold rotation axis and resides in the cavities of the rigid [Ca10(PO4)7](-) framework. It is surrounded by three O atoms in an almost regular triangular environment.

Related literature

For the structure of the mineral whitlockite, see: Calvo & Gopal (1975 ▶); Yashima et al. (2003 ▶). For powder diffraction studies and Rietveld refinements of phosphate-based whitlockite-related compounds, see: Lazoryak et al. (1996 ▶); Morozov et al. (2000 ▶, 2002 ▶); Zatovsky et al. (2007 ▶, 2010 ▶, 2011 ▶). For physical properties of these materials, see: Dou et al. (2011 ▶); Enhai et al. (2011 ▶); Lazoryak et al. (2004 ▶); Teterskii et al. (2005 ▶); Zhang et al. (2011 ▶). For the crystal structure of isotypic KCa10(PO4)7, see: Sandström & Boström (2006 ▶). For bond-valence calculations, see: Brown (2002 ▶).

Experimental

Crystal data

AgCa10(PO4)7

M = 1173.46

Trigonal,

a = 10.43723 (5) Å

c = 37.3379 (7) Å

V = 3522.50 (7) Å3

Z = 6

Cu Kα radiation, λ = 1.540560 Å

T = 293 K

Flat sheet, 25 × 25 mm

Data collection

Shimadzu LabX XRD-6000 diffractometer

Specimen mounting: glass container

Data collection mode: reflection

Scan method: step

2θmin = 9.045°, 2θmax = 100.045°, 2θstep = 0.020°

Refinement

R p = 0.094

R wp = 0.125

R exp = 0.042

R Bragg = 0.051

R(F) = 0.038

χ2 = 8.821

4551 data points

150 parameters

3 restraints

Data collection: PCXRD (Shimadzu, 2006 ▶); cell refinement: DICVOL (Boultif & Louër, 2004 ▶); data reduction: FULLPROF (Rodriguez-Carvajal, 2006 ▶); program(s) used to solve structure: FULLPROF (Rodriguez-Carvajal, 2006 ▶); program(s) used to refine structure: FULLPROF (Rodriguez-Carvajal, 2006 ▶); molecular graphics: DIAMOND (Brandenburg, 1999 ▶); software used to prepare material for publication: PLATON (Spek, 2009 ▶) and enCIFer (Allen et al., 2004 ▶).

Click here for additional data file.

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536813007848/wm2726sup1.cif

Click here for additional data file.

Rietveld powder data: contains datablock(s) I. DOI: 10.1107/S1600536813007848/wm2726Isup2.rtv

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

AgCa10(PO4)7	Dx = 3.319 Mg m−3
Mr = 1173.46	Cu Kα radiation, λ = 1.540560 Å
Trigonal, R3c	T = 293 K
Hall symbol: R 3 -2"c	Particle morphology: isometric
a = 10.43723 (5) Å	white
c = 37.3379 (7) Å	flat sheet, 25 × 25 mm
V = 3522.50 (7) Å3	Specimen preparation: Prepared at 293 K and 101.3 kPa
Z = 6

Shimadzu LabX XRD-6000 diffractometer	Data collection mode: reflection
Radiation source: X-ray tube, X-ray	Scan method: step
Graphite monochromator	2θmin = 9.045°, 2θmax = 100.045°, 2θstep = 0.020°
Specimen mounting: glass container

Rp = 0.094	150 parameters
Rwp = 0.125	3 restraints
Rexp = 0.042	3 constraints
RBragg = 0.051	Standard least squares refinement
R(F) = 0.038	(Δ/σ)max = 0.001
χ2 = 8.821	Background function: Linear Interpolation between a set background points with refinable heights
4551 data points	Preferred orientation correction: March-Dollase Numeric Multiaxial Function
Profile function: Pearson VII

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles

	x	y	z	Uiso*/Ueq
Ag1	0.00000	0.00000	0.1780 (8)	0.042 (2)*
Ca1	0.33333	0.66667	0.1632 (9)	0.002 (2)*
Ca2	0.4650 (10)	0.5260 (11)	0.0955 (8)	0.0044 (14)*
Ca3	0.2864 (7)	0.1558 (12)	0.0625 (8)	0.004 (2)*
Ca4	0.3992 (5)	0.1876 (9)	0.1565 (8)	0.0044 (14)*
P1	0.66667	0.33333	0.0976 (8)	0.002 (4)*
P2	0.1577 (14)	0.3495 (13)	0.0288 (8)	0.009 (3)*
P3	0.1366 (11)	0.3111 (7)	0.1306 (8)	0.003 (3)*
O1	0.66667	0.33333	0.1387 (11)	0.006 (11)*
O2	0.5229 (16)	0.325 (2)	0.0860 (9)	0.006 (6)*
O3	0.082 (3)	0.1873 (15)	0.0421 (9)	0.005 (3)*
O4	0.051 (2)	0.394 (3)	0.0420 (10)	0.005 (3)*
O5	0.173 (2)	0.3689 (18)	−0.0111 (9)	0.005 (3)*
O6	0.316 (2)	0.440 (2)	0.0462 (10)	0.005 (3)*
O7	−0.0093 (19)	0.267 (3)	0.1100 (9)	0.006 (4)*
O8	0.241 (3)	0.4824 (13)	0.1261 (9)	0.006 (4)*
O9	0.221 (2)	0.243 (3)	0.1161 (10)	0.006 (4)*
O10	0.0887 (18)	0.267 (2)	0.1700 (10)	0.006 (4)*

	U11	U22	U33	U12	U13	U23
?	?	?	?	?	?	?

Ag1—O10	2.476 (19)	Ca3—O4ii	2.62 (4)
Ag1—O10i	2.476 (19)	Ca3—O6	2.89 (3)
Ag1—O10ii	2.476 (19)	Ca4—O7ii	2.40 (4)
Ca1—O8	2.17 (4)	Ca4—O6ix	2.45 (4)
Ca1—O8iii	2.17 (4)	Ca4—O4vi	2.46 (4)
Ca1—O8iv	2.17 (4)	Ca4—O1	2.510 (14)
Ca1—O3v	2.40 (4)	Ca4—O5ix	2.55 (3)
Ca1—O3vi	2.40 (4)	Ca4—O5vi	2.59 (2)
Ca1—O3vii	2.40 (4)	Ca4—O9	2.67 (4)
Ca2—O6	2.28 (4)	Ca4—O10ii	2.692 (18)
Ca2—O5vi	2.41 (4)	Ca4—O2	2.97 (4)
Ca2—O8	2.43 (4)	P1—O1	1.54 (5)
Ca2—O4iii	2.45 (4)	P1—O2	1.52 (2)
Ca2—O2	2.48 (3)	P1—O2x	1.52 (2)
Ca2—O8iii	2.48 (3)	P1—O2xi	1.52 (2)
Ca2—O7iii	2.57 (2)	P2—O3	1.55 (2)
Ca2—O9	2.88 (3)	P2—O4	1.49 (3)
Ca3—O7ii	2.31 (4)	P2—O5	1.50 (4)
Ca3—O3ii	2.37 (2)	P2—O6	1.58 (3)
Ca3—O2	2.37 (2)	P3—O7	1.56 (3)
Ca3—O9	2.43 (4)	P3—O8	1.570 (15)
Ca3—O3	2.44 (4)	P3—O9	1.48 (3)
Ca3—O10viii	2.46 (4)	P3—O10	1.55 (5)
O10—Ag1—O10i	118.5 (9)	O1—P1—O2x	106.6 (17)
O10—Ag1—O10ii	118.6 (7)	O2x—P1—O2xi	112.3 (18)
O10i—Ag1—O10ii	118.6 (8)	O2—P1—O2x	112.2 (16)
O7—P3—O8	107.7 (19)	O2—P1—O2xi	112.2 (17)
O7—P3—O9	114 (2)	O3—P2—O4	101 (2)
O7—P3—O10	105.0 (17)	O4—P2—O5	109 (2)
O8—P3—O9	105.5 (18)	O3—P2—O5	115.3 (19)
O8—P3—O10	112 (2)	O3—P2—O6	109 (2)
O9—P3—O10	112.7 (19)	O4—P2—O6	114 (2)
O1—P1—O2xi	106.5 (16)	O5—P2—O6	108.6 (19)
O1—P1—O2	106.5 (16)	Ag1—O10—P3	109.4 (15)