Download citation
Download citation
link to html
Nonacalcium chromium(III) hepta­kis(orthophosphate) has been obtained from a melt in the system Cs2O–CaO–Cr2O3 using a polyphosphate flux. The three-dimensional framework is related to the whitlockite structure [β-Ca3(PO4)3] and is built up from CaO8 and CaO9 polyhedra sharing vertices, edges and faces, further connected by PO4 tetra­hedra and CrO6 octa­hedra. The Cr, one P and one O atom are located on threefold rotation axes. Ca9Cr(PO4)7 is isotypic with Ca9Fe(PO4)7. The crystal studied was an inversion twin.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807044765/wm2144sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536807044765/wm2144Isup2.hkl
Contains datablock I

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • Mean [sigma](P-O) = 0.003 Å
  • R factor = 0.030
  • wR factor = 0.073
  • Data-to-parameter ratio = 15.8

checkCIF/PLATON results

No syntax errors found



Alert level B PLAT430_ALERT_2_B Short Inter D...A Contact O1 .. O10 .. 2.63 Ang. PLAT430_ALERT_2_B Short Inter D...A Contact O1 .. O10 .. 2.63 Ang. PLAT430_ALERT_2_B Short Inter D...A Contact O1 .. O10 .. 2.63 Ang. PLAT430_ALERT_2_B Short Inter D...A Contact O6 .. O6 .. 2.68 Ang. PLAT430_ALERT_2_B Short Inter D...A Contact O6 .. O6 .. 2.68 Ang.
Alert level C STRVA01_ALERT_4_C Flack test results are ambiguous. From the CIF: _refine_ls_abs_structure_Flack 0.590 From the CIF: _refine_ls_abs_structure_Flack_su 0.040 PLAT041_ALERT_1_C Calc. and Rep. SumFormula Strings Differ .... ? PLAT045_ALERT_1_C Calculated and Reported Z Differ by ............ 0.33 Ratio PLAT094_ALERT_2_C Ratio of Maximum / Minimum Residual Density .... 2.11 PLAT430_ALERT_2_C Short Inter D...A Contact O2 .. O4 .. 2.89 Ang. PLAT430_ALERT_2_C Short Inter D...A Contact O7 .. O8 .. 2.88 Ang.
Alert level G REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is correct. If it is not, please give the correct count in the _publ_section_exptl_refinement section of the submitted CIF. From the CIF: _diffrn_reflns_theta_max 29.99 From the CIF: _reflns_number_total 2161 Count of symmetry unique reflns 1121 Completeness (_total/calc) 192.77% TEST3: Check Friedels for noncentro structure Estimate of Friedel pairs measured 1040 Fraction of Friedel pairs measured 0.928 Are heavy atom types Z>Si present yes PLAT033_ALERT_2_G Flack Parameter Value Deviates 2 * su from zero. 0.59 PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature 293 K PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature . 293 K PLAT794_ALERT_5_G Check Predicted Bond Valency for Cr1 (3) 2.71 PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints ....... 1
0 ALERT level A = In general: serious problem 5 ALERT level B = Potentially serious problem 6 ALERT level C = Check and explain 6 ALERT level G = General alerts; check 4 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 9 ALERT type 2 Indicator that the structure model may be wrong or deficient 1 ALERT type 3 Indicator that the structure quality may be low 2 ALERT type 4 Improvement, methodology, query or suggestion 1 ALERT type 5 Informative message, check

Comment top

Partial substitution of alkaline earth metal atoms in MII3(PO4)2 (MII = Ca, Sr) whitlockite-type structures (Dickens et al., 1974) by monovalent, bivalent and tetravalent metals provides possibilities for obtaining new compounds with useful properties. This group of orthophosphates and their solid solutions have been intensively studied and are interesting in aspects of applications. For example, Ca9In(PO4)7 (Morozov et al., 2002), Ca9RE(PO4)7 (RE = rare-earth metals) (Teterskii et al., 2005) and Ca9Fe(PO4)7 (Lazoryak et al., 2004) exhibit interesting dielectric properties and large second-harmonic generation (SHG) effects; the solid solutions Sr9.2Co1.3(PO4)7 (Belik et al., 2006), Ca3 - xCox(PO4)2 (Legrouri et al., 1996) and Ca3 - xCux(PO4)2 (Benarafa et al., 2000) possess catalytic activity; Ca9Fe(PO4)7 (Lazoryak et al., 1996) can be used as a sensor material and for removing H2 from gas mixtures.

We report here the flux-growth synthesis and structural characterization of the whitlockite-related phosphate Ca9Cr(PO4)7, (I), which is isotypic with Ca9Fe(PO4)7 (Lazoryak et al., 2004).

The structure of (I) contains three types of layers, which are formed by Ca atoms in positions Ca1, Ca2 and Ca3, respectively (Fig. 1). The Ca1O8, Ca2O8 and Ca3O9 polyhedra, with Ca–O distances ranging from 2.316 (3) to 2.913 (3) Å (Table), are linked together via vertices, edges and faces. The polyhedral network is additionally linked by three different corner- or edge-sharing PO4 tetrahedra and a CrO6 octahedron. The PO4 tetrahedra are quite regular with P–O bond lengths ranging from 1.508 (3) to 1.584 (3) Å, and O–P–O angles spreading over the range 104.58 (16)–114.19 (18)°. The coordination of the Cr3+ cation is slightly distorted octahedral with two different Cr–O distances of 2.012 (3) and 2.023 (3) Å, respectively (Fig. 3).

Related literature top

For the structure of whitlockite (β-Ca3(PO4)2), see: Dickens et al. (1974). For related whitlockite-type phosphates, see: Morozov et al. (2002) Ca9In(PO4)7; Teterskii et al. (2005) Ca9RE(PO4)7 (RE = rare earth metals); Lazoryak et al. (1996, 2004) Ca9Fe(PO4)7; Belik et al. (2006) Sr9.2Co1.3(PO4)7; Legrouri et al. (1996) Ca3 - xCox(PO4)2; Benarafa et al. (2000) Ca3 - xCux(PO4)2.

Experimental top

The title compound was prepared in a flux in the system Cs2O—P2O5—CaO-Cr2O3. A mixture of CsPO3 (5.0 g), CaCO3 (0.708 g) and Cr2O3 (0.270 g) was ground in an agate mortar, placed into a platinum crucible and heated up to 1273 K. The melt was kept at this temperature until it became homogenous (2 h). The temperature was then decreased to 1053 K at a rate of 30 K h-1, and at this temperature the remaining flux was decantated. Finally, the crucible was cooled down to room temperature. The solidified melt was leached out with deionized water and light-green crystals of Ca9Cr(PO4)7 were recovered.

Refinement top

The measured crystal was racemically twinned (Flack parameter 0.59 (4)). The highest remaining peak in the final Fourier map is 0.82 Å from atom P1.

Structure description top

Partial substitution of alkaline earth metal atoms in MII3(PO4)2 (MII = Ca, Sr) whitlockite-type structures (Dickens et al., 1974) by monovalent, bivalent and tetravalent metals provides possibilities for obtaining new compounds with useful properties. This group of orthophosphates and their solid solutions have been intensively studied and are interesting in aspects of applications. For example, Ca9In(PO4)7 (Morozov et al., 2002), Ca9RE(PO4)7 (RE = rare-earth metals) (Teterskii et al., 2005) and Ca9Fe(PO4)7 (Lazoryak et al., 2004) exhibit interesting dielectric properties and large second-harmonic generation (SHG) effects; the solid solutions Sr9.2Co1.3(PO4)7 (Belik et al., 2006), Ca3 - xCox(PO4)2 (Legrouri et al., 1996) and Ca3 - xCux(PO4)2 (Benarafa et al., 2000) possess catalytic activity; Ca9Fe(PO4)7 (Lazoryak et al., 1996) can be used as a sensor material and for removing H2 from gas mixtures.

We report here the flux-growth synthesis and structural characterization of the whitlockite-related phosphate Ca9Cr(PO4)7, (I), which is isotypic with Ca9Fe(PO4)7 (Lazoryak et al., 2004).

The structure of (I) contains three types of layers, which are formed by Ca atoms in positions Ca1, Ca2 and Ca3, respectively (Fig. 1). The Ca1O8, Ca2O8 and Ca3O9 polyhedra, with Ca–O distances ranging from 2.316 (3) to 2.913 (3) Å (Table), are linked together via vertices, edges and faces. The polyhedral network is additionally linked by three different corner- or edge-sharing PO4 tetrahedra and a CrO6 octahedron. The PO4 tetrahedra are quite regular with P–O bond lengths ranging from 1.508 (3) to 1.584 (3) Å, and O–P–O angles spreading over the range 104.58 (16)–114.19 (18)°. The coordination of the Cr3+ cation is slightly distorted octahedral with two different Cr–O distances of 2.012 (3) and 2.023 (3) Å, respectively (Fig. 3).

For the structure of whitlockite (β-Ca3(PO4)2), see: Dickens et al. (1974). For related whitlockite-type phosphates, see: Morozov et al. (2002) Ca9In(PO4)7; Teterskii et al. (2005) Ca9RE(PO4)7 (RE = rare earth metals); Lazoryak et al. (1996, 2004) Ca9Fe(PO4)7; Belik et al. (2006) Sr9.2Co1.3(PO4)7; Legrouri et al. (1996) Ca3 - xCox(PO4)2; Benarafa et al. (2000) Ca3 - xCux(PO4)2.

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2005); cell refinement: CrysAlis CCD (Oxford Diffraction, 2005); data reduction: CrysAlis RED (Oxford Diffraction, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. Unit cell with the three types of calcium layers in the crystal structure of (I). Colour code: Pink plane – Ca1 layer, green plane – Ca2 layer, red plane – Ca3 layer; green octahedra – CrO6 polyhedra, purple tetrahedra – PO4).
[Figure 2] Fig. 2. The Ca2+ cations with their oxygen neighbours, displayed with anisotropic displacement ellipsoids at the 70% probability level [Symmetry code: (ii) -x + y, -x, z; (v) 2/3 - x + y, 1/3 + y, -1/6 + z; (vi) 1/3 + x, 2/3 + x-y, 1/6 + z; (vii) 1/3 - x + y, -1/3 + y, 1/6 + z; (viii) 2/3 - y, 1/3 - x, -1/6 + z; (x) 2/3 - y, 1/3 + x-y, -1/3 + z; (xi) 1/3 - y, 2/3 - y, 1/6 + z.].
[Figure 3] Fig. 3. Fragment of the crystal structure of (I) showing the coordination of the Cr3+ cation. The CaO8 polyhedra are displayed with grey shading, PO4 tetrahedra with purple shading and Cr atom as green circle.
Nonacalcium chromium(III) heptakis(orthophosphate) top
Crystal data top
Ca9Cr(PO4)7Dx = 3.13 Mg m3
Mr = 1077.51Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3cCell parameters from 8460 reflections
Hall symbol: R 3 -2"cθ = 3.2–30.0°
a = 10.3272 (5) ŵ = 3.14 mm1
c = 37.132 (2) ÅT = 293 K
V = 3429.6 (3) Å3Prism, green
Z = 60.07 × 0.07 × 0.05 mm
F(000) = 3198
Data collection top
XCalibur-3 CCD (Oxford Diffraction)
diffractometer
2161 independent reflections
Radiation source: fine-focus sealed tube1814 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.035
φ and ω scansθmax = 30.0°, θmin = 3.2°
Absorption correction: multi-scan
MULABS (Blessing, 1995)
h = 1414
Tmin = 0.810, Tmax = 0.859k = 1414
8460 measured reflectionsl = 4652
Refinement top
Refinement on F21 restraint
Least-squares matrix: full w = 1/[σ2(Fo2) + (0.0394P)2]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.030(Δ/σ)max < 0.001
wR(F2) = 0.073Δρmax = 1.78 e Å3
S = 1.10Δρmin = 0.84 e Å3
2161 reflectionsAbsolute structure: Flack (1983), 1040 Friedel pairs
137 parametersAbsolute structure parameter: 0.59 (4)
Crystal data top
Ca9Cr(PO4)7Z = 6
Mr = 1077.51Mo Kα radiation
Trigonal, R3cµ = 3.14 mm1
a = 10.3272 (5) ÅT = 293 K
c = 37.132 (2) Å0.07 × 0.07 × 0.05 mm
V = 3429.6 (3) Å3
Data collection top
XCalibur-3 CCD (Oxford Diffraction)
diffractometer
2161 independent reflections
Absorption correction: multi-scan
MULABS (Blessing, 1995)
1814 reflections with I > 2σ(I)
Tmin = 0.810, Tmax = 0.859Rint = 0.035
8460 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0301 restraint
wR(F2) = 0.073Δρmax = 1.78 e Å3
S = 1.10Δρmin = 0.84 e Å3
2161 reflectionsAbsolute structure: Flack (1983), 1040 Friedel pairs
137 parametersAbsolute structure parameter: 0.59 (4)
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Ca10.05547 (9)0.52061 (10)0.100572 (19)0.00617 (17)
Ca20.20187 (10)0.37769 (10)0.23313 (2)0.00654 (17)
Ca30.38876 (10)0.20333 (9)0.16032 (2)0.01017 (17)
Cr1000.00199 (3)0.00405 (18)
P1000.27062 (5)0.0106 (4)
P20.17511 (12)0.31774 (12)0.13731 (3)0.0042 (2)
P30.18862 (12)0.34253 (14)0.03226 (3)0.0052 (2)
O1000.31204 (16)0.0148 (11)
O20.1360 (3)0.1467 (3)0.25799 (8)0.0111 (6)
O30.1821 (4)0.2731 (4)0.17561 (8)0.0121 (6)
O40.0164 (3)0.2525 (4)0.12245 (8)0.0103 (6)
O50.2744 (3)0.2782 (3)0.11421 (7)0.0076 (6)
O60.2502 (4)0.4937 (3)0.13402 (8)0.0083 (6)
O70.3479 (3)0.3948 (3)0.04562 (8)0.0097 (6)
O80.1122 (3)0.4133 (3)0.05284 (8)0.0101 (6)
O90.0940 (3)0.1692 (3)0.03804 (8)0.0076 (6)
O100.1937 (3)0.3779 (3)0.00752 (7)0.0097 (6)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ca10.0074 (4)0.0061 (4)0.0053 (4)0.0036 (3)0.0003 (3)0.0012 (3)
Ca20.0062 (4)0.0071 (4)0.0060 (3)0.0032 (4)0.0011 (3)0.0020 (3)
Ca30.0151 (4)0.0082 (4)0.0091 (4)0.0072 (3)0.0035 (3)0.0001 (3)
Cr10.0040 (3)0.0040 (3)0.0042 (4)0.00199 (13)00
P10.0060 (5)0.0060 (5)0.0199 (10)0.0030 (2)00
P20.0037 (5)0.0030 (4)0.0058 (5)0.0016 (4)0.0007 (4)0.0006 (4)
P30.0060 (5)0.0049 (4)0.0046 (5)0.0026 (4)0.0020 (4)0.0008 (4)
O10.0126 (16)0.0126 (16)0.019 (3)0.0063 (8)00
O20.0055 (13)0.0057 (14)0.0184 (18)0.0002 (10)0.0037 (11)0.0035 (11)
O30.0149 (15)0.0126 (15)0.0095 (15)0.0075 (12)0.0002 (12)0.0003 (11)
O40.0080 (15)0.0141 (15)0.0080 (15)0.0050 (12)0.0004 (11)0.0001 (11)
O50.0073 (14)0.0053 (13)0.0098 (14)0.0028 (11)0.0017 (10)0.0026 (11)
O60.0081 (14)0.0075 (14)0.0107 (14)0.0050 (13)0.0007 (11)0.0001 (10)
O70.0031 (13)0.0131 (15)0.0111 (15)0.0026 (12)0.0008 (11)0.0012 (12)
O80.0142 (15)0.0103 (14)0.0099 (14)0.0091 (13)0.0025 (11)0.0023 (11)
O90.0058 (14)0.0030 (13)0.0129 (14)0.0014 (12)0.0001 (11)0.0010 (11)
O100.0128 (15)0.0097 (14)0.0031 (13)0.0031 (12)0.0016 (11)0.0005 (10)
Geometric parameters (Å, º) top
Ca1—O82.316 (3)Ca3—P3vi3.0244 (14)
Ca1—O10i2.352 (3)Ca3—P23.0987 (14)
Ca1—O2ii2.404 (3)Ca3—P3v3.1244 (14)
Ca1—O7iii2.477 (3)Cr1—O6ix2.012 (3)
Ca1—O5iii2.480 (3)Cr1—O6viii2.012 (3)
Ca1—O62.495 (3)Cr1—O6ii2.012 (3)
Ca1—O6iii2.513 (3)Cr1—O9x2.023 (3)
Ca1—O42.716 (3)Cr1—O9vii2.023 (3)
Ca1—P2iii3.1171 (14)Cr1—O92.023 (3)
Ca1—P23.2195 (14)P1—O2x1.536 (3)
Ca1—P1iv3.4804 (9)P1—O21.536 (3)
Ca1—Ca2ii3.4861 (10)P1—O2vii1.536 (3)
Ca2—O22.320 (3)P1—O11.538 (6)
Ca2—O32.356 (3)P1—Ca3i3.2507 (15)
Ca2—O5i2.386 (3)P1—Ca3xi3.2507 (16)
Ca2—O9i2.471 (3)P1—Ca3vi3.2508 (15)
Ca2—O4v2.474 (3)P1—Ca1xii3.4803 (9)
Ca2—O9v2.503 (3)P1—Ca1v3.4804 (9)
Ca2—O7i2.590 (3)P1—Ca1xiii3.4804 (9)
Ca2—O8v2.630 (3)P2—O31.508 (3)
Ca2—P3i3.1141 (15)P2—O41.530 (3)
Ca2—P3v3.1424 (14)P2—O51.540 (3)
Ca2—Ca1v3.4862 (10)P2—O61.584 (3)
Ca2—Cr1i3.5254 (12)P2—Ca1xiv3.1171 (14)
Ca3—O7vi2.398 (3)P2—Ca3x3.5400 (13)
Ca3—O52.417 (3)P3—O101.516 (3)
Ca3—O4vii2.457 (3)P3—O81.522 (3)
Ca3—O10v2.497 (3)P3—O71.535 (3)
Ca3—O1viii2.5484 (16)P3—O91.567 (3)
Ca3—O10vi2.577 (3)P3—Ca3xv3.0244 (14)
Ca3—O32.633 (3)P3—Ca2viii3.1141 (15)
Ca3—O8v2.645 (3)P3—Ca3ii3.1244 (14)
Ca3—O2viii2.913 (3)P3—Ca2ii3.1424 (14)
O8—Ca1—O10i142.88 (11)O1viii—Ca3—O2viii53.59 (14)
O8—Ca1—O2ii84.88 (11)O10vi—Ca3—O2viii65.06 (9)
O10i—Ca1—O2ii77.14 (10)O3—Ca3—O2viii130.12 (10)
O8—Ca1—O7iii73.68 (10)O8v—Ca3—O2viii141.78 (9)
O10i—Ca1—O7iii138.10 (10)O6ix—Cr1—O6viii83.53 (13)
O2ii—Ca1—O7iii91.57 (10)O6ix—Cr1—O6ii83.53 (13)
O8—Ca1—O5iii141.13 (11)O6viii—Cr1—O6ii83.53 (13)
O10i—Ca1—O5iii74.37 (10)O6ix—Cr1—O9x98.93 (13)
O2ii—Ca1—O5iii98.61 (10)O6viii—Cr1—O9x177.54 (15)
O7iii—Ca1—O5iii67.56 (9)O6ii—Cr1—O9x96.57 (12)
O8—Ca1—O685.21 (11)O6ix—Cr1—O9vii96.57 (12)
O10i—Ca1—O679.07 (10)O6viii—Cr1—O9vii98.93 (13)
O2ii—Ca1—O6124.72 (10)O6ii—Cr1—O9vii177.54 (15)
O7iii—Ca1—O6136.30 (10)O9x—Cr1—O9vii80.98 (13)
O5iii—Ca1—O6121.53 (10)O6ix—Cr1—O9177.54 (15)
O8—Ca1—O6iii124.59 (11)O6viii—Cr1—O996.57 (12)
O10i—Ca1—O6iii77.97 (10)O6ii—Cr1—O998.93 (13)
O2ii—Ca1—O6iii150.53 (10)O9x—Cr1—O980.98 (13)
O7iii—Ca1—O6iii96.50 (10)O9vii—Cr1—O980.98 (13)
O5iii—Ca1—O6iii59.32 (10)O2x—P1—O2111.11 (12)
O6—Ca1—O6iii64.72 (14)O2x—P1—O2vii111.11 (12)
O8—Ca1—O471.64 (10)O2—P1—O2vii111.11 (12)
O10i—Ca1—O471.58 (10)O2x—P1—O1107.78 (13)
O2ii—Ca1—O468.34 (10)O2—P1—O1107.78 (13)
O7iii—Ca1—O4141.05 (10)O2vii—P1—O1107.78 (13)
O5iii—Ca1—O4145.46 (10)O3—P2—O4114.19 (18)
O6—Ca1—O456.93 (10)O3—P2—O5107.73 (17)
O6iii—Ca1—O4117.61 (10)O4—P2—O5113.00 (17)
O8—Ca1—P2iii143.40 (9)O3—P2—O6110.64 (18)
O2—Ca2—O388.61 (11)O4—P2—O6106.27 (17)
O2—Ca2—O5i84.27 (11)O5—P2—O6104.58 (16)
O3—Ca2—O5i142.23 (11)P1—O1—Ca3i102.58 (13)
O2—Ca2—O9i157.39 (11)P1—O1—Ca3xi102.58 (13)
O3—Ca2—O9i88.49 (11)Ca3i—O1—Ca3xi115.40 (9)
O5i—Ca2—O9i84.36 (10)P1—O1—Ca3vi102.58 (13)
O2—Ca2—O4v73.98 (10)Ca3i—O1—Ca3vi115.39 (9)
O3—Ca2—O4v139.97 (12)Ca3xi—O1—Ca3vi115.39 (9)
O5i—Ca2—O4v72.72 (11)P1—O2—Ca2142.12 (19)
O9i—Ca2—O4v120.70 (11)P1—O2—Ca1v122.56 (17)
O2—Ca2—O9v137.71 (11)Ca2—O2—Ca1v95.10 (10)
O3—Ca2—O9v81.44 (10)P1—O2—Ca3i88.21 (14)
O5i—Ca2—O9v126.71 (10)Ca2—O2—Ca3i86.29 (9)
O9i—Ca2—O9v63.75 (14)Ca1v—O2—Ca3i92.17 (9)
O4v—Ca2—O9v87.73 (10)P2—O3—Ca2136.17 (19)
O2—Ca2—O7i98.25 (10)P2—O3—Ca392.84 (15)
O3—Ca2—O7i77.37 (11)Ca2—O3—Ca3115.12 (13)
O5i—Ca2—O7i67.12 (10)P2—O4—Ca3x123.57 (16)
O9i—Ca2—O7i59.26 (10)P2—O4—Ca2ii142.26 (17)
O4v—Ca2—O7i139.70 (10)Ca3x—O4—Ca2ii93.97 (11)
O9v—Ca2—O7i119.04 (10)P2—O4—Ca194.49 (15)
O2—Ca2—O8v79.84 (10)Ca3x—O4—Ca195.96 (11)
O3—Ca2—O8v70.70 (11)Ca2ii—O4—Ca184.28 (9)
O5i—Ca2—O8v143.05 (10)P2—O5—Ca2viii147.59 (18)
O9i—Ca2—O8v120.07 (10)P2—O5—Ca3100.77 (14)
O4v—Ca2—O8v70.88 (10)Ca2viii—O5—Ca397.29 (11)
O9v—Ca2—O8v58.03 (9)P2—O5—Ca1xiv98.99 (14)
O7i—Ca2—O8v148.04 (10)Ca2viii—O5—Ca1xiv103.64 (11)
O7vi—Ca3—O5153.05 (12)Ca3—O5—Ca1xiv101.18 (11)
O7vi—Ca3—O4vii94.92 (11)P2—O6—Cr1i135.74 (18)
O5—Ca3—O4vii72.50 (10)P2—O6—Ca1101.92 (15)
O7vi—Ca3—O10v123.00 (10)Cr1i—O6—Ca1103.22 (13)
O5—Ca3—O10v72.96 (10)P2—O6—Ca1xiv96.44 (15)
O4vii—Ca3—O10v142.08 (10)Cr1i—O6—Ca1xiv102.60 (13)
O7vi—Ca3—O1viii100.65 (13)Ca1—O6—Ca1xiv118.58 (12)
O5—Ca3—O1viii106.20 (13)P3—O7—Ca3xv98.15 (14)
O4vii—Ca3—O1viii113.31 (12)P3—O7—Ca1xiv130.55 (17)
O10v—Ca3—O1viii62.91 (7)Ca3xv—O7—Ca1xiv109.05 (12)
O7vi—Ca3—O10vi59.84 (9)P3—O7—Ca2viii94.56 (14)
O5—Ca3—O10vi133.01 (9)Ca3xv—O7—Ca2viii130.06 (13)
O4vii—Ca3—O10vi72.52 (10)Ca1xiv—O7—Ca2viii98.01 (10)
O10v—Ca3—O10vi123.73 (12)P3—O8—Ca1158.44 (19)
O1viii—Ca3—O10vi61.84 (7)P3—O8—Ca2ii94.58 (15)
O7vi—Ca3—O3101.93 (11)Ca1—O8—Ca2ii89.39 (10)
O5—Ca3—O358.15 (10)P3—O8—Ca3ii93.18 (14)
O4vii—Ca3—O398.18 (11)Ca1—O8—Ca3ii106.09 (12)
O10v—Ca3—O376.22 (10)Ca2ii—O8—Ca3ii105.99 (11)
O1viii—Ca3—O3139.12 (8)P3—O9—Cr1130.69 (17)
O10vi—Ca3—O3157.60 (11)P3—O9—Ca2viii98.43 (14)
O7vi—Ca3—O8v69.36 (10)Cr1—O9—Ca2viii102.88 (13)
O5—Ca3—O8v112.01 (10)P3—O9—Ca2ii98.45 (14)
O4vii—Ca3—O8v153.80 (11)Cr1—O9—Ca2ii101.80 (12)
O10v—Ca3—O8v57.68 (9)Ca2viii—O9—Ca2ii128.60 (12)
O1viii—Ca3—O8v90.72 (13)P3—O10—Ca1viii145.17 (19)
O10vi—Ca3—O8v113.31 (9)P3—O10—Ca3ii99.33 (15)
O3—Ca3—O8v66.48 (10)Ca1viii—O10—Ca3ii102.53 (10)
O7vi—Ca3—O2viii124.77 (10)P3—O10—Ca3xv91.55 (13)
O5—Ca3—O2viii71.97 (10)Ca1viii—O10—Ca3xv102.52 (11)
O4vii—Ca3—O2viii64.38 (9)Ca3ii—O10—Ca3xv116.21 (12)
O10v—Ca3—O2viii90.31 (9)
Symmetry codes: (i) y+1/3, x+2/3, z+1/6; (ii) x1/3, xy+1/3, z1/6; (iii) x+y, x+1, z; (iv) y1/3, x+1/3, z1/6; (v) x+1/3, xy+2/3, z+1/6; (vi) x+y+1/3, y1/3, z+1/6; (vii) x+y, x, z; (viii) y+2/3, x+1/3, z1/6; (ix) x+y1/3, y2/3, z1/6; (x) y, xy, z; (xi) x2/3, xy1/3, z+1/6; (xii) x+y2/3, y1/3, z+1/6; (xiii) y+1/3, x1/3, z+1/6; (xiv) y+1, xy+1, z; (xv) x+y+2/3, y+1/3, z1/6.

Experimental details

Crystal data
Chemical formulaCa9Cr(PO4)7
Mr1077.51
Crystal system, space groupTrigonal, R3c
Temperature (K)293
a, c (Å)10.3272 (5), 37.132 (2)
V3)3429.6 (3)
Z6
Radiation typeMo Kα
µ (mm1)3.14
Crystal size (mm)0.07 × 0.07 × 0.05
Data collection
DiffractometerXCalibur-3 CCD (Oxford Diffraction)
Absorption correctionMulti-scan
MULABS (Blessing, 1995)
Tmin, Tmax0.810, 0.859
No. of measured, independent and
observed [I > 2σ(I)] reflections
8460, 2161, 1814
Rint0.035
(sin θ/λ)max1)0.703
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.030, 0.073, 1.10
No. of reflections2161
No. of parameters137
No. of restraints1
Δρmax, Δρmin (e Å3)1.78, 0.84
Absolute structureFlack (1983), 1040 Friedel pairs
Absolute structure parameter0.59 (4)

Computer programs: CrysAlis CCD (Oxford Diffraction, 2005), CrysAlis RED (Oxford Diffraction, 2005), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), DIAMOND (Brandenburg, 2006), WinGX (Farrugia, 1999).

Selected bond lengths (Å) top
Ca1—O82.316 (3)Ca3—O10iv2.497 (3)
Ca1—O10i2.352 (3)Ca3—O1vii2.5484 (16)
Ca1—O2ii2.404 (3)Ca3—O10v2.577 (3)
Ca1—O7iii2.477 (3)Ca3—O32.633 (3)
Ca1—O5iii2.480 (3)Ca3—O8iv2.645 (3)
Ca1—O62.495 (3)Ca3—O2vii2.913 (3)
Ca1—O6iii2.513 (3)Cr1—O6viii2.012 (3)
Ca1—O42.716 (3)Cr1—O92.023 (3)
Ca2—O22.320 (3)P1—O21.536 (3)
Ca2—O32.356 (3)P1—O11.538 (6)
Ca2—O5i2.386 (3)P2—O31.508 (3)
Ca2—O9i2.471 (3)P2—O41.530 (3)
Ca2—O4iv2.474 (3)P2—O51.540 (3)
Ca2—O9iv2.503 (3)P2—O61.584 (3)
Ca2—O7i2.590 (3)P3—O101.516 (3)
Ca2—O8iv2.630 (3)P3—O81.522 (3)
Ca3—O7v2.398 (3)P3—O71.535 (3)
Ca3—O52.417 (3)P3—O91.567 (3)
Ca3—O4vi2.457 (3)
Symmetry codes: (i) y+1/3, x+2/3, z+1/6; (ii) x1/3, xy+1/3, z1/6; (iii) x+y, x+1, z; (iv) x+1/3, xy+2/3, z+1/6; (v) x+y+1/3, y1/3, z+1/6; (vi) x+y, x, z; (vii) y+2/3, x+1/3, z1/6; (viii) x+y1/3, y2/3, z1/6.
 

Follow Acta Cryst. E
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds