Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270113000723/bi3051sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270113000723/bi3051Isup2.hkl |
The title compound, originally described under an oxide formula 9CaO.4CrO3.Cr2O3, is congruently melting at 1501 K and its primary crystallization field (PCF) was found in compositions from 44 to 53 wt% Cr2O3 in the CaO–Cr2O3 system in air (Ford et al., 1949). Three samples (denoted 1, 2 and 3) within the indicated PCF were prepared from CaCO3, CrO3, HNO3 and H2O containing 46, 49 and 51 wt% Cr2O3, respectively (Figusch & Pánek, 1976). Aqueous solutions of the starting materials were evaporated to dryness and the dry residues subsequently decomposed by slow heating up to 1173 K. X-ray powder diffraction patterns showed the presence of Ca5(CrO4)3OH and CaCrO4 at this stage. Portions of the samples (from 10 to 15 g) were heated in a Pt crucible to 1523 K, held there for 3 h, then cooled at a controlled cooling rate of 50 K h-1 to a temperature of 1453 (sample 1) or 1323 K (samples 2 and 3), then cooled to room temperature by removal from the furnace. Inspection of crushed samples revealed fragments of crystals of the title compound with an edge size up to 1 mm. The crystals are opaque, black, dark-green translucent in thin layers and show conchoidal fracture. In samples 2 and 3, minor amounts of CaCrO4 were also observed, in disagreement with the pseudobinary phase diagram by Ford et al. (1949), which may indicate a nonequilibrium with a higher content of oxygen in the melt.
The refinement could not proceed successfuly until racemic twin treatment of the data was introduced, which converged to refined volume fractions 0.53 (3):0.47 (3). The site occupancies of Cr3A/Cr3B and O3A/O3B in the disordered CrO4 group were constrained to the same (and complementary) values.
Data collection: SMART (Bruker, 2003); cell refinement: SAINT (Bruker, 2003); data reduction: SAINT (Bruker, 2003) and SADABS (Sheldrick, 2003); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2012); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).
Ca10(CrO4)6(CrO4) | Dx = 3.166 Mg m−3 |
Mr = 1212.80 | Mo Kα radiation, λ = 0.71073 Å |
Trigonal, R3c | Cell parameters from 8192 reflections |
Hall symbol: R 3 -2"c | θ = 2.4–28.3° |
a = 10.7580 (1) Å | µ = 5.01 mm−1 |
c = 38.0730 (3) Å | T = 183 K |
V = 3816.02 (6) Å3 | Pyramid, dark-green |
Z = 6 | 0.09 × 0.08 × 0.08 mm |
F(000) = 3552 |
Siemens SMART CCD area-detector diffractometer | 2034 independent reflections |
Radiation source: fine-focus sealed tube | 1918 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.036 |
ω scans | θmax = 28.3°, θmin = 2.4° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | h = −14→14 |
Tmin = 0.661, Tmax = 0.690 | k = −14→14 |
13345 measured reflections | l = −48→49 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.024 | w = 1/[σ2(Fo2) + (0.0367P)2 + 8.2518P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.060 | (Δ/σ)max < 0.001 |
S = 1.04 | Δρmax = 0.47 e Å−3 |
2034 reflections | Δρmin = −0.66 e Å−3 |
144 parameters | Absolute structure: Flack (1983), 995 Friedel pairs |
1 restraint | Absolute structure parameter: 0.53 (3) |
Ca10(CrO4)6(CrO4) | Z = 6 |
Mr = 1212.80 | Mo Kα radiation |
Trigonal, R3c | µ = 5.01 mm−1 |
a = 10.7580 (1) Å | T = 183 K |
c = 38.0730 (3) Å | 0.09 × 0.08 × 0.08 mm |
V = 3816.02 (6) Å3 |
Siemens SMART CCD area-detector diffractometer | 2034 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | 1918 reflections with I > 2σ(I) |
Tmin = 0.661, Tmax = 0.690 | Rint = 0.036 |
13345 measured reflections |
R[F2 > 2σ(F2)] = 0.024 | 1 restraint |
wR(F2) = 0.060 | Δρmax = 0.47 e Å−3 |
S = 1.04 | Δρmin = −0.66 e Å−3 |
2034 reflections | Absolute structure: Flack (1983), 995 Friedel pairs |
144 parameters | Absolute structure parameter: 0.53 (3) |
Experimental. Data were collected at low temperature using a Siemens SMART CCD diffractometer equiped with a LT-2 device. A full sphere of reciprocal space was scanned by 0.3° steps in ω with a crystal–to–detector distance of 5.0 cm, 15 s per frame. Preliminary orientation matrix was obtained from the first 100 frames using SMART (Bruker, 2003). The collected frames were integrated using the preliminary orientation matrix which was updated every 100 frames. Final cell parameters were obtained by refinement on the position of 8192 reflections with I>10σ(I) after integration of all the frames data using SAINT (Bruker, 2003). |
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. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Ca1 | 0.28499 (9) | 0.15823 (8) | −0.06050 (2) | 0.01475 (17) | |
Ca2 | 0.19733 (9) | −0.19629 (9) | 0.00064 (2) | 0.00867 (17) | |
Ca3 | 0.38785 (9) | 0.18174 (8) | 0.034490 (19) | 0.00836 (17) | |
Ca4 | 0.6667 | 0.3333 | 0.10044 (5) | 0.0110 (2) | |
Cr1 | 0.31082 (7) | 0.13996 (7) | 0.132847 (13) | 0.00709 (14) | |
Cr2 | 0.17809 (7) | −0.13622 (7) | −0.099116 (13) | 0.00704 (14) | |
Cr3A | 0.0000 | 0.0000 | 0.00182 (5) | 0.0075 (6) | 0.695 (6) |
Cr3B | 0.0000 | 0.0000 | 0.02671 (13) | 0.0118 (13) | 0.305 (6) |
O3A | 0.0000 | 0.0000 | −0.0419 (2) | 0.0152 (17) | 0.695 (6) |
O3B | 0.0000 | 0.0000 | 0.0673 (5) | 0.019 (4) | 0.305 (6) |
O1 | 0.2825 (3) | 0.0882 (3) | 0.09083 (7) | 0.0195 (6) | |
O2 | 0.2354 (3) | 0.2354 (3) | 0.14633 (7) | 0.0147 (6) | |
O3 | 0.2772 (3) | −0.0159 (3) | 0.15446 (6) | 0.0101 (5) | |
O4 | 0.4905 (3) | 0.2456 (3) | 0.14215 (8) | 0.0106 (6) | |
O5 | 0.1515 (4) | −0.1249 (4) | −0.05569 (8) | 0.0239 (8) | |
O6 | 0.2564 (3) | −0.2373 (3) | −0.10949 (8) | 0.0107 (6) | |
O7 | 0.3013 (3) | 0.0339 (3) | −0.11153 (7) | 0.0123 (5) | |
O8 | 0.0148 (3) | −0.2215 (3) | −0.11737 (7) | 0.0177 (6) | |
O9 | −0.0044 (4) | 0.1451 (3) | 0.01383 (9) | 0.0171 (5) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Ca1 | 0.0210 (4) | 0.0150 (4) | 0.0120 (3) | 0.0118 (3) | −0.0049 (3) | −0.0044 (3) |
Ca2 | 0.0077 (4) | 0.0101 (4) | 0.0078 (3) | 0.0041 (3) | −0.0007 (3) | −0.0019 (3) |
Ca3 | 0.0075 (4) | 0.0080 (4) | 0.0082 (3) | 0.0028 (3) | −0.0023 (3) | −0.0015 (3) |
Ca4 | 0.0141 (3) | 0.0141 (3) | 0.0049 (4) | 0.00703 (16) | 0.000 | 0.000 |
Cr1 | 0.0061 (3) | 0.0084 (3) | 0.0064 (3) | 0.0034 (2) | 0.0015 (2) | 0.0007 (3) |
Cr2 | 0.0072 (3) | 0.0082 (3) | 0.0062 (3) | 0.0042 (2) | −0.0003 (3) | −0.0008 (3) |
Cr3A | 0.0057 (6) | 0.0057 (6) | 0.0111 (14) | 0.0028 (3) | 0.000 | 0.000 |
Cr3B | 0.0097 (14) | 0.0097 (14) | 0.016 (3) | 0.0048 (7) | 0.000 | 0.000 |
O3A | 0.016 (2) | 0.016 (2) | 0.014 (4) | 0.0079 (12) | 0.000 | 0.000 |
O3B | 0.024 (6) | 0.024 (6) | 0.009 (9) | 0.012 (3) | 0.000 | 0.000 |
O1 | 0.0284 (16) | 0.0243 (17) | 0.0094 (12) | 0.0160 (15) | −0.0017 (12) | −0.0007 (12) |
O2 | 0.0171 (14) | 0.0209 (15) | 0.0134 (13) | 0.0150 (12) | 0.0048 (11) | 0.0042 (11) |
O3 | 0.0084 (12) | 0.0067 (12) | 0.0113 (12) | 0.0007 (11) | 0.0006 (9) | 0.0003 (9) |
O4 | 0.0065 (13) | 0.0079 (12) | 0.0160 (15) | 0.0025 (11) | 0.0003 (12) | −0.0007 (10) |
O5 | 0.0262 (17) | 0.0248 (17) | 0.0065 (13) | 0.0021 (14) | 0.0011 (12) | 0.0010 (11) |
O6 | 0.0077 (12) | 0.0077 (13) | 0.0168 (15) | 0.0038 (11) | 0.0020 (11) | 0.0020 (11) |
O7 | 0.0150 (13) | 0.0070 (12) | 0.0130 (12) | 0.0040 (11) | 0.0030 (11) | 0.0016 (10) |
O8 | 0.0098 (14) | 0.0288 (16) | 0.0120 (13) | 0.0078 (13) | −0.0013 (11) | 0.0036 (12) |
O9 | 0.0185 (12) | 0.0133 (14) | 0.0244 (13) | 0.0116 (13) | 0.0070 (10) | 0.0016 (12) |
Ca1—O3i | 2.364 (3) | Cr1—O3 | 1.736 (3) |
Ca1—O7 | 2.414 (3) | Cr1—Ca1vi | 3.1588 (10) |
Ca1—O2ii | 2.502 (3) | Cr1—Ca2iv | 3.1744 (9) |
Ca1—O8iii | 2.537 (3) | Cr1—Ca2viii | 3.3877 (10) |
Ca1—O1i | 2.592 (3) | Cr1—Ca1viii | 3.7043 (10) |
Ca1—O5iii | 2.609 (3) | Cr2—O8 | 1.673 (3) |
Ca1—O5 | 2.646 (3) | Cr2—O5 | 1.693 (3) |
Ca1—O3A | 2.753 (2) | Cr2—O7 | 1.704 (3) |
Ca1—Cr2 | 3.1426 (9) | Cr2—O6 | 1.722 (3) |
Ca1—Cr1i | 3.1586 (10) | Cr2—Ca1vii | 3.1984 (10) |
Ca1—Cr2iii | 3.1985 (10) | Cr2—Ca3ii | 3.2173 (10) |
Ca1—Cr3A | 3.5650 (15) | Cr2—Ca3v | 3.2996 (10) |
Ca2—O8iv | 2.339 (3) | Cr2—Ca4ii | 3.5207 (9) |
Ca2—O5 | 2.410 (3) | Cr2—Ca2i | 3.6295 (10) |
Ca2—O4ii | 2.424 (3) | Cr3A—Cr3B | 0.947 (4) |
Ca2—O4v | 2.437 (3) | Cr3A—O3A | 1.666 (8) |
Ca2—O7vi | 2.442 (3) | Cr3A—O9 | 1.650 (2) |
Ca2—O3v | 2.472 (3) | Cr3A—O9vii | 1.650 (2) |
Ca2—O9vii | 2.508 (3) | Cr3A—O9iii | 1.650 (2) |
Ca2—O2ii | 3.004 (3) | Cr3A—Ca1iii | 3.5651 (15) |
Ca2—Cr1v | 3.1745 (9) | Cr3A—Ca1vii | 3.5651 (15) |
Ca2—Cr1ii | 3.3878 (10) | Cr3A—Ca2iii | 3.6674 (9) |
Ca2—Ca4ii | 3.5990 (14) | Cr3A—Ca2vii | 3.6675 (9) |
Ca2—Cr2vi | 3.6293 (10) | Cr3B—O3B | 1.547 (18) |
Ca3—O3i | 2.354 (3) | Cr3B—O9 | 1.659 (3) |
Ca3—O1 | 2.400 (3) | Cr3B—O9vii | 1.659 (3) |
Ca3—O2ii | 2.411 (3) | Cr3B—O9iii | 1.659 (3) |
Ca3—O6viii | 2.413 (3) | Cr3B—Ca3iii | 3.6280 (10) |
Ca3—O9vii | 2.438 (3) | Cr3B—Ca3vii | 3.6280 (10) |
Ca3—O6iv | 2.453 (3) | O3A—Ca1iii | 2.753 (2) |
Ca3—O7viii | 2.703 (3) | O3A—Ca1vii | 2.753 (2) |
Ca3—O8iv | 2.865 (3) | O1—Ca1vi | 2.592 (3) |
Ca3—Cr2viii | 3.2172 (10) | O2—Ca3viii | 2.410 (3) |
Ca3—Cr2iv | 3.2996 (10) | O2—Ca1viii | 2.502 (3) |
Ca3—Ca4 | 3.6151 (14) | O2—Ca2viii | 3.004 (3) |
Ca3—Cr3B | 3.6280 (10) | O3—Ca3vi | 2.354 (3) |
Ca4—O4ix | 2.284 (3) | O3—Ca1vi | 2.365 (3) |
Ca4—O4x | 2.284 (3) | O3—Ca2iv | 2.472 (3) |
Ca4—O4 | 2.284 (3) | O4—Ca2viii | 2.424 (3) |
Ca4—O6xi | 2.307 (3) | O4—Ca2iv | 2.437 (3) |
Ca4—O6iv | 2.307 (3) | O5—Ca1vii | 2.609 (3) |
Ca4—O6viii | 2.307 (3) | O6—Ca4ii | 2.307 (3) |
Ca4—Cr2xi | 3.5207 (9) | O6—Ca3ii | 2.413 (3) |
Ca4—Cr2iv | 3.5207 (9) | O6—Ca3v | 2.453 (3) |
Ca4—Cr2viii | 3.5206 (9) | O7—Ca2i | 2.443 (3) |
Ca4—Cr1ix | 3.5414 (9) | O7—Ca3ii | 2.703 (3) |
Ca4—Cr1x | 3.5414 (9) | O8—Ca2v | 2.339 (3) |
Ca4—Cr1 | 3.5414 (9) | O8—Ca1vii | 2.537 (3) |
Cr1—O1 | 1.671 (3) | O8—Ca3v | 2.865 (3) |
Cr1—O2 | 1.675 (3) | O9—Ca3iii | 2.438 (3) |
Cr1—O4 | 1.719 (3) | O9—Ca2iii | 2.508 (3) |
O3i—Ca1—O7 | 155.86 (11) | O4ix—Ca4—Cr1x | 97.15 (8) |
O3i—Ca1—O2ii | 68.57 (10) | O4x—Ca4—Cr1x | 23.80 (7) |
O7—Ca1—O2ii | 96.83 (9) | O4—Ca4—Cr1x | 93.65 (8) |
O3i—Ca1—O8iii | 120.10 (10) | O6xi—Ca4—Cr1x | 85.01 (6) |
O7—Ca1—O8iii | 66.60 (10) | O6iv—Ca4—Cr1x | 154.81 (9) |
O2ii—Ca1—O8iii | 156.37 (12) | O6viii—Ca4—Cr1x | 85.90 (6) |
O3i—Ca1—O1i | 64.66 (9) | Cr2xi—Ca4—Cr1x | 70.853 (16) |
O7—Ca1—O1i | 101.07 (9) | Cr2iv—Ca4—Cr1x | 178.92 (3) |
O2ii—Ca1—O1i | 100.06 (10) | Cr2viii—Ca4—Cr1x | 72.539 (17) |
O8iii—Ca1—O1i | 68.70 (9) | Cr1ix—Ca4—Cr1x | 108.54 (3) |
O3i—Ca1—O5iii | 73.59 (10) | O4ix—Ca4—Cr1 | 93.65 (8) |
O7—Ca1—O5iii | 125.09 (10) | O4x—Ca4—Cr1 | 97.15 (8) |
O2ii—Ca1—O5iii | 137.55 (10) | O4—Ca4—Cr1 | 23.80 (7) |
O8iii—Ca1—O5iii | 62.98 (9) | O6xi—Ca4—Cr1 | 154.81 (9) |
O1i—Ca1—O5iii | 79.95 (9) | O6iv—Ca4—Cr1 | 85.90 (6) |
O3i—Ca1—O5 | 124.77 (9) | O6viii—Ca4—Cr1 | 85.01 (6) |
O7—Ca1—O5 | 64.26 (9) | Cr2xi—Ca4—Cr1 | 178.92 (3) |
O2ii—Ca1—O5 | 73.07 (10) | Cr2iv—Ca4—Cr1 | 72.541 (17) |
O8iii—Ca1—O5 | 111.07 (10) | Cr2viii—Ca4—Cr1 | 70.853 (17) |
O1i—Ca1—O5 | 162.11 (12) | Cr1ix—Ca4—Cr1 | 108.54 (3) |
O5iii—Ca1—O5 | 116.47 (16) | Cr1x—Ca4—Cr1 | 108.54 (3) |
O3i—Ca1—O3A | 99.74 (15) | O1—Cr1—O2 | 115.72 (15) |
O7—Ca1—O3A | 103.35 (14) | O1—Cr1—O3 | 102.52 (14) |
O2ii—Ca1—O3A | 109.47 (14) | O1—Cr1—O4 | 112.02 (15) |
O8iii—Ca1—O3A | 91.32 (15) | O2—Cr1—O3 | 121.04 (14) |
O1i—Ca1—O3A | 138.66 (7) | O2—Cr1—O4 | 105.11 (14) |
O5iii—Ca1—O3A | 58.72 (8) | O4—Cr1—O3 | 99.38 (13) |
O5—Ca1—O3A | 58.32 (8) | O1—Cr1—Ca1vi | 55.02 (11) |
O3i—Ca1—Cr2 | 154.94 (7) | O2—Cr1—Ca1vi | 137.31 (11) |
O7—Ca1—Cr2 | 32.47 (6) | O4—Cr1—Ca1vi | 117.00 (10) |
O2ii—Ca1—Cr2 | 89.15 (7) | O3—Cr1—Ca1vi | 47.56 (9) |
O8iii—Ca1—Cr2 | 84.91 (7) | O1—Cr1—Ca2iv | 110.00 (11) |
O1i—Ca1—Cr2 | 133.54 (7) | O2—Cr1—Ca2iv | 133.87 (10) |
O5iii—Ca1—Cr2 | 121.74 (9) | O4—Cr1—Ca2iv | 49.46 (9) |
O5—Ca1—Cr2 | 32.59 (6) | O3—Cr1—Ca2iv | 50.71 (9) |
O3A—Ca1—Cr2 | 76.33 (9) | Ca1vi—Cr1—Ca2iv | 75.87 (3) |
O3i—Ca1—Cr1i | 32.81 (6) | O1—Cr1—Ca2viii | 129.41 (12) |
O7—Ca1—Cr1i | 129.89 (7) | O2—Cr1—Ca2viii | 62.40 (11) |
O2ii—Ca1—Cr1i | 82.79 (7) | O4—Cr1—Ca2viii | 42.73 (9) |
O8iii—Ca1—Cr1i | 94.97 (7) | O3—Cr1—Ca2viii | 121.80 (9) |
O1i—Ca1—Cr1i | 31.88 (6) | Ca1vi—Cr1—Ca2viii | 159.25 (3) |
O5iii—Ca1—Cr1i | 75.48 (8) | Ca2iv—Cr1—Ca2viii | 84.30 (4) |
O5—Ca1—Cr1i | 153.94 (8) | O1—Cr1—Ca4 | 79.96 (11) |
O3A—Ca1—Cr1i | 124.13 (9) | O2—Cr1—Ca4 | 117.33 (10) |
Cr2—Ca1—Cr1i | 159.50 (4) | O4—Cr1—Ca4 | 32.41 (11) |
O3i—Ca1—Cr2iii | 95.93 (7) | O3—Cr1—Ca4 | 111.99 (10) |
O7—Ca1—Cr2iii | 96.60 (7) | Ca1vi—Cr1—Ca4 | 102.58 (2) |
O2ii—Ca1—Cr2iii | 164.17 (7) | Ca2iv—Cr1—Ca4 | 64.54 (3) |
O8iii—Ca1—Cr2iii | 31.29 (7) | Ca2viii—Cr1—Ca4 | 62.54 (2) |
O1i—Ca1—Cr2iii | 69.06 (7) | O1—Cr1—Ca1viii | 84.32 (11) |
O5iii—Ca1—Cr2iii | 31.88 (7) | O2—Cr1—Ca1viii | 34.17 (9) |
O5—Ca1—Cr2iii | 120.68 (8) | O4—Cr1—Ca1viii | 107.47 (9) |
O3A—Ca1—Cr2iii | 75.39 (9) | O3—Cr1—Ca1viii | 147.48 (10) |
Cr2—Ca1—Cr2iii | 106.69 (3) | Ca1vi—Cr1—Ca1viii | 127.73 (3) |
Cr1i—Ca1—Cr2iii | 82.17 (2) | Ca2iv—Cr1—Ca1viii | 155.68 (3) |
O3i—Ca1—Cr3A | 76.53 (7) | Ca2viii—Cr1—Ca1viii | 71.55 (2) |
O7—Ca1—Cr3A | 123.67 (7) | Ca4—Cr1—Ca1viii | 100.47 (2) |
O2ii—Ca1—Cr3A | 88.38 (7) | O8—Cr2—O5 | 106.06 (15) |
O8iii—Ca1—Cr3A | 114.63 (8) | O8—Cr2—O7 | 120.89 (14) |
O1i—Ca1—Cr3A | 133.23 (7) | O5—Cr2—O7 | 105.20 (14) |
O5iii—Ca1—Cr3A | 64.30 (7) | O8—Cr2—O6 | 105.61 (15) |
O5—Ca1—Cr3A | 64.03 (7) | O5—Cr2—O6 | 115.04 (17) |
O3A—Ca1—Cr3A | 26.85 (16) | O7—Cr2—O6 | 104.56 (13) |
Cr2—Ca1—Cr3A | 92.07 (3) | O8—Cr2—Ca1 | 120.14 (11) |
Cr1i—Ca1—Cr3A | 106.44 (3) | O5—Cr2—Ca1 | 57.34 (11) |
Cr2iii—Ca1—Cr3A | 91.15 (3) | O7—Cr2—Ca1 | 49.53 (9) |
O8iv—Ca2—O5 | 139.87 (12) | O6—Cr2—Ca1 | 134.11 (10) |
O8iv—Ca2—O4ii | 80.30 (10) | O8—Cr2—Ca1vii | 51.96 (10) |
O5—Ca2—O4ii | 86.37 (11) | O5—Cr2—Ca1vii | 54.50 (11) |
O8iv—Ca2—O4v | 120.21 (11) | O7—Cr2—Ca1vii | 135.81 (10) |
O5—Ca2—O4v | 90.27 (11) | O6—Cr2—Ca1vii | 119.51 (9) |
O4ii—Ca2—O4v | 71.59 (13) | Ca1—Cr2—Ca1vii | 93.22 (4) |
O8iv—Ca2—O7vi | 69.30 (10) | O8—Cr2—Ca3ii | 129.76 (10) |
O5—Ca2—O7vi | 137.44 (11) | O5—Cr2—Ca3ii | 123.34 (12) |
O4ii—Ca2—O7vi | 135.50 (10) | O7—Cr2—Ca3ii | 57.14 (10) |
O4v—Ca2—O7vi | 96.15 (10) | O6—Cr2—Ca3ii | 47.44 (8) |
O8iv—Ca2—O3v | 139.00 (10) | Ca1—Cr2—Ca3ii | 95.70 (3) |
O5—Ca2—O3v | 75.38 (10) | Ca1vii—Cr2—Ca3ii | 166.36 (3) |
O4ii—Ca2—O3v | 132.25 (10) | O8—Cr2—Ca3v | 60.26 (11) |
O4v—Ca2—O3v | 64.92 (9) | O5—Cr2—Ca3v | 117.10 (11) |
O7vi—Ca2—O3v | 69.70 (9) | O7—Cr2—Ca3v | 135.70 (9) |
O8iv—Ca2—O9vii | 80.92 (11) | O6—Cr2—Ca3v | 46.39 (9) |
O5—Ca2—O9vii | 75.01 (12) | Ca1—Cr2—Ca3v | 174.43 (3) |
O4ii—Ca2—O9vii | 122.89 (9) | Ca1vii—Cr2—Ca3v | 82.88 (3) |
O4v—Ca2—O9vii | 157.66 (10) | Ca3ii—Cr2—Ca3v | 87.45 (3) |
O7vi—Ca2—O9vii | 84.25 (10) | O8—Cr2—Ca4ii | 120.09 (11) |
O3v—Ca2—O9vii | 94.69 (9) | O5—Cr2—Ca4ii | 81.02 (14) |
O8iv—Ca2—O2ii | 72.83 (8) | O7—Cr2—Ca4ii | 113.41 (9) |
O5—Ca2—O2ii | 67.96 (9) | O6—Cr2—Ca4ii | 34.10 (11) |
O4ii—Ca2—O2ii | 58.39 (9) | Ca1—Cr2—Ca4ii | 113.33 (3) |
O4v—Ca2—O2ii | 125.62 (9) | Ca1vii—Cr2—Ca4ii | 102.22 (3) |
O7vi—Ca2—O2ii | 133.97 (9) | Ca3ii—Cr2—Ca4ii | 64.71 (3) |
O3v—Ca2—O2ii | 141.28 (10) | Ca3v—Cr2—Ca4ii | 63.92 (2) |
O9vii—Ca2—O2ii | 64.58 (9) | O8—Cr2—Ca2i | 86.90 (10) |
O8iv—Ca2—Cr1v | 141.77 (9) | O5—Cr2—Ca2i | 128.07 (12) |
O5—Ca2—Cr1v | 77.79 (8) | O7—Cr2—Ca2i | 35.17 (9) |
O4ii—Ca2—Cr1v | 100.61 (7) | O6—Cr2—Ca2i | 108.79 (10) |
O4v—Ca2—Cr1v | 32.43 (7) | Ca1—Cr2—Ca2i | 72.48 (2) |
O7vi—Ca2—Cr1v | 85.51 (7) | Ca1vii—Cr2—Ca2i | 122.06 (3) |
O3v—Ca2—Cr1v | 32.92 (6) | Ca3ii—Cr2—Ca2i | 70.69 (2) |
O9vii—Ca2—Cr1v | 125.96 (7) | Ca3v—Cr2—Ca2i | 112.96 (3) |
O2ii—Ca2—Cr1v | 140.00 (6) | Ca4ii—Cr2—Ca2i | 135.35 (3) |
O8iv—Ca2—Cr1ii | 75.14 (8) | Cr3B—Cr3A—O3A | 180.0 |
O5—Ca2—Cr1ii | 75.14 (8) | Cr3B—Cr3A—O9 | 73.91 (13) |
O4ii—Ca2—Cr1ii | 28.77 (7) | O3A—Cr3A—O9 | 106.09 (13) |
O4v—Ca2—Cr1ii | 98.21 (7) | Cr3B—Cr3A—O9 | 73.91 (13) |
O7vi—Ca2—Cr1ii | 144.22 (7) | O3A—Cr3A—O9vii | 106.09 (13) |
O3v—Ca2—Cr1ii | 145.74 (7) | O9—Cr3A—O9vii | 112.63 (11) |
O9vii—Ca2—Cr1ii | 94.18 (7) | Cr3B—Cr3A—O9iii | 73.91 (13) |
O2ii—Ca2—Cr1ii | 29.62 (6) | O3A—Cr3A—O9iii | 106.09 (13) |
Cr1v—Ca2—Cr1ii | 122.33 (3) | O9—Cr3A—O9iii | 112.63 (11) |
O8iv—Ca2—Ca4ii | 114.58 (8) | O9vii—Cr3A—O9iii | 112.63 (11) |
O5—Ca2—Ca4ii | 72.00 (9) | Cr3B—Cr3A—Ca1 | 131.73 (3) |
O4ii—Ca2—Ca4ii | 38.73 (7) | O3A—Cr3A—Ca1 | 48.27 (3) |
O4v—Ca2—Ca4ii | 38.78 (7) | O9—Cr3A—Ca1 | 99.05 (12) |
O7vi—Ca2—Ca4ii | 132.54 (7) | O9vii—Cr3A—Ca1 | 65.01 (12) |
O3v—Ca2—Ca4ii | 93.53 (6) | O9iii—Cr3A—Ca1 | 144.94 (13) |
O9vii—Ca2—Ca4ii | 142.64 (9) | Cr3B—Cr3A—Ca1iii | 131.73 (3) |
O2ii—Ca2—Ca4ii | 86.87 (6) | O3A—Cr3A—Ca1iii | 48.27 (3) |
Cr1v—Ca2—Ca4ii | 62.676 (18) | O9—Cr3A—Ca1iii | 65.01 (12) |
Cr1ii—Ca2—Ca4ii | 60.822 (16) | O9vii—Cr3A—Ca1iii | 144.94 (13) |
O8iv—Ca2—Cr2vi | 77.25 (8) | O9iii—Cr3A—Ca1iii | 99.05 (12) |
O5—Ca2—Cr2vi | 140.63 (8) | Ca1—Cr3A—Ca1iii | 80.53 (4) |
O4ii—Ca2—Cr2vi | 119.65 (7) | Cr3B—Cr3A—Ca1vii | 131.73 (3) |
O4v—Ca2—Cr2vi | 73.18 (8) | O3A—Cr3A—Ca1vii | 48.27 (3) |
O7vi—Ca2—Cr2vi | 23.69 (6) | O9—Cr3A—Ca1vii | 144.94 (13) |
O3v—Ca2—Cr2vi | 65.26 (6) | O9vii—Cr3A—Ca1vii | 99.05 (12) |
O9vii—Ca2—Cr2vi | 107.69 (8) | O9iii—Cr3A—Ca1vii | 65.01 (12) |
O2ii—Ca2—Cr2vi | 149.90 (6) | Ca1—Cr3A—Ca1vii | 80.53 (4) |
Cr1v—Ca2—Cr2vi | 69.150 (19) | Ca1iii—Cr3A—Ca1vii | 80.52 (4) |
Cr1ii—Ca2—Cr2vi | 141.28 (3) | Cr3B—Cr3A—Ca2iii | 90.71 (3) |
Ca4ii—Ca2—Cr2vi | 108.85 (3) | O3A—Cr3A—Ca2iii | 89.29 (3) |
O3i—Ca3—O1 | 140.50 (10) | O9—Cr3A—Ca2iii | 35.25 (12) |
O3i—Ca3—O2ii | 70.30 (10) | O9vii—Cr3A—Ca2iii | 88.86 (12) |
O1—Ca3—O2ii | 139.16 (11) | O9iii—Cr3A—Ca2iii | 147.88 (13) |
O3i—Ca3—O6viii | 84.89 (10) | Ca1—Cr3A—Ca2iii | 65.12 (2) |
O1—Ca3—O6viii | 94.64 (11) | Ca1iii—Cr3A—Ca2iii | 70.09 (2) |
O2ii—Ca3—O6viii | 118.65 (11) | Ca1vii—Cr3A—Ca2iii | 137.44 (5) |
O3i—Ca3—O9vii | 82.67 (11) | Cr3B—Cr3A—Ca2 | 90.70 (3) |
O1—Ca3—O9vii | 82.45 (11) | O3A—Cr3A—Ca2 | 89.30 (3) |
O2ii—Ca3—O9vii | 75.68 (10) | O9—Cr3A—Ca2 | 147.87 (13) |
O6viii—Ca3—O9vii | 156.26 (10) | O9vii—Cr3A—Ca2 | 35.24 (12) |
O3i—Ca3—O6iv | 131.27 (10) | O9iii—Cr3A—Ca2 | 88.86 (12) |
O1—Ca3—O6iv | 84.30 (10) | Ca1—Cr3A—Ca2 | 70.10 (2) |
O2ii—Ca3—O6iv | 85.60 (10) | Ca1iii—Cr3A—Ca2 | 137.44 (5) |
O6viii—Ca3—O6iv | 70.17 (14) | Ca1vii—Cr3A—Ca2 | 65.12 (2) |
O9vii—Ca3—O6iv | 132.42 (10) | Ca2iii—Cr3A—Ca2 | 119.985 (1) |
O3i—Ca3—O7viii | 67.06 (9) | Cr3B—Cr3A—Ca2vii | 90.71 (3) |
O1—Ca3—O7viii | 77.38 (9) | O3A—Cr3A—Ca2vii | 89.29 (3) |
O2ii—Ca3—O7viii | 136.91 (10) | O9—Cr3A—Ca2vii | 88.86 (12) |
O6viii—Ca3—O7viii | 63.67 (9) | O9vii—Cr3A—Ca2vii | 147.87 (13) |
O9vii—Ca3—O7viii | 92.81 (9) | O9iii—Cr3A—Ca2vii | 35.24 (12) |
O6iv—Ca3—O7viii | 128.17 (9) | Ca1—Cr3A—Ca2vii | 137.44 (5) |
O3i—Ca3—O8iv | 140.88 (9) | Ca1iii—Cr3A—Ca2vii | 65.12 (2) |
O1—Ca3—O8iv | 66.01 (10) | Ca1vii—Cr3A—Ca2vii | 70.09 (2) |
O2ii—Ca3—O8iv | 74.58 (8) | Ca2iii—Cr3A—Ca2vii | 119.985 (1) |
O6viii—Ca3—O8iv | 127.95 (10) | Ca2—Cr3A—Ca2vii | 119.985 (1) |
O9vii—Ca3—O8iv | 72.33 (10) | Cr3A—Cr3B—O3B | 180.0 |
O6iv—Ca3—O8iv | 60.54 (10) | Cr3A—Cr3B—O9 | 72.8 (2) |
O7viii—Ca3—O8iv | 141.72 (9) | O3B—Cr3B—O9 | 107.2 (2) |
O3i—Ca3—Cr2viii | 74.23 (7) | Cr3A—Cr3B—O9vii | 72.8 (2) |
O1—Ca3—Cr2viii | 84.84 (8) | O3B—Cr3B—O9vii | 107.2 (2) |
O2ii—Ca3—Cr2viii | 135.89 (8) | O9—Cr3B—O9vii | 111.66 (18) |
O6viii—Ca3—Cr2viii | 31.71 (7) | Cr3A—Cr3B—O9iii | 72.8 (2) |
O9vii—Ca3—Cr2viii | 124.76 (7) | O3B—Cr3B—O9iii | 107.2 (2) |
O6iv—Ca3—Cr2viii | 99.09 (7) | O9—Cr3B—O9iii | 111.66 (18) |
O7viii—Ca3—Cr2viii | 31.97 (6) | O9vii—Cr3B—O9iii | 111.66 (18) |
O8iv—Ca3—Cr2viii | 144.89 (6) | Cr3A—Cr3B—Ca3 | 94.68 (8) |
O3i—Ca3—Cr2iv | 150.08 (7) | O3B—Cr3B—Ca3 | 85.32 (8) |
O1—Ca3—Cr2iv | 69.21 (7) | O9—Cr3B—Ca3 | 94.77 (12) |
O2ii—Ca3—Cr2iv | 82.44 (7) | O9vii—Cr3B—Ca3 | 34.06 (13) |
O6viii—Ca3—Cr2iv | 98.09 (8) | O9iii—Cr3B—Ca3 | 144.85 (14) |
O9vii—Ca3—Cr2iv | 102.78 (8) | Cr3A—Cr3B—Ca3iii | 94.68 (8) |
O6iv—Ca3—Cr2iv | 30.55 (7) | O3B—Cr3B—Ca3iii | 85.32 (8) |
O7viii—Ca3—Cr2iv | 140.51 (6) | O9—Cr3B—Ca3iii | 34.06 (13) |
O8iv—Ca3—Cr2iv | 30.46 (6) | O9vii—Cr3B—Ca3iii | 144.85 (14) |
Cr2viii—Ca3—Cr2iv | 121.98 (3) | O9iii—Cr3B—Ca3iii | 94.77 (12) |
O3i—Ca3—Ca4 | 122.79 (7) | Ca3—Cr3B—Ca3iii | 119.34 (2) |
O1—Ca3—Ca4 | 71.32 (8) | Cr3A—Cr3B—Ca3vii | 94.68 (8) |
O2ii—Ca3—Ca4 | 119.86 (8) | O3B—Cr3B—Ca3vii | 85.32 (8) |
O6viii—Ca3—Ca4 | 38.94 (8) | O9—Cr3B—Ca3vii | 144.84 (14) |
O9vii—Ca3—Ca4 | 152.63 (9) | O9vii—Cr3B—Ca3vii | 94.77 (12) |
O6iv—Ca3—Ca4 | 39.09 (7) | O9iii—Cr3B—Ca3vii | 34.06 (13) |
O7viii—Ca3—Ca4 | 89.09 (6) | Ca3—Cr3B—Ca3vii | 119.34 (2) |
O8iv—Ca3—Ca4 | 89.50 (6) | Ca3iii—Cr3B—Ca3vii | 119.34 (2) |
Cr2viii—Ca3—Ca4 | 61.709 (17) | Cr3A—O3A—Ca1 | 104.88 (16) |
Cr2iv—Ca3—Ca4 | 61.014 (17) | Cr3A—O3A—Ca1iii | 104.88 (16) |
O3i—Ca3—Cr3B | 81.86 (9) | Ca1—O3A—Ca1iii | 113.65 (13) |
O1—Ca3—Cr3B | 70.86 (10) | Cr3A—O3A—Ca1vii | 104.88 (16) |
O2ii—Ca3—Cr3B | 96.52 (10) | Ca1—O3A—Ca1vii | 113.65 (13) |
O6viii—Ca3—Cr3B | 135.24 (8) | Ca1iii—O3A—Ca1vii | 113.64 (13) |
O9vii—Ca3—Cr3B | 22.41 (9) | Cr1—O1—Ca3 | 138.31 (18) |
O6iv—Ca3—Cr3B | 144.29 (8) | Cr1—O1—Ca1vi | 93.10 (12) |
O7viii—Ca3—Cr3B | 71.79 (6) | Ca3—O1—Ca1vi | 118.96 (12) |
O8iv—Ca3—Cr3B | 85.57 (7) | Cr1—O2—Ca3viii | 136.61 (15) |
Cr2viii—Ca3—Cr3B | 103.62 (4) | Cr1—O2—Ca1viii | 123.73 (14) |
Cr2iv—Ca3—Cr3B | 114.18 (4) | Ca3viii—O2—Ca1viii | 99.64 (11) |
Ca4—Ca3—Cr3B | 140.45 (8) | Cr1—O2—Ca2viii | 87.98 (12) |
O4ix—Ca4—O4x | 76.98 (12) | Ca3viii—O2—Ca2viii | 86.96 (9) |
O4ix—Ca4—O4 | 76.98 (12) | Ca1viii—O2—Ca2viii | 97.55 (9) |
O4x—Ca4—O4 | 76.98 (12) | Cr1—O3—Ca3vi | 134.78 (15) |
O4ix—Ca4—O6xi | 105.92 (9) | Cr1—O3—Ca1vi | 99.63 (11) |
O4x—Ca4—O6xi | 102.53 (9) | Ca3vi—O3—Ca1vi | 105.41 (10) |
O4—Ca4—O6xi | 176.93 (11) | Cr1—O3—Ca2iv | 96.38 (12) |
O4ix—Ca4—O6iv | 102.53 (9) | Ca3vi—O3—Ca2iv | 110.90 (10) |
O4x—Ca4—O6iv | 176.93 (11) | Ca1vi—O3—Ca2iv | 107.19 (11) |
O4—Ca4—O6iv | 105.92 (9) | Cr1—O4—Ca4 | 123.79 (16) |
O6xi—Ca4—O6iv | 74.63 (12) | Cr1—O4—Ca2viii | 108.49 (13) |
O4ix—Ca4—O6viii | 176.93 (11) | Ca4—O4—Ca2viii | 99.67 (10) |
O4x—Ca4—O6viii | 105.92 (9) | Cr1—O4—Ca2iv | 98.11 (12) |
O4—Ca4—O6viii | 102.53 (9) | Ca4—O4—Ca2iv | 99.29 (10) |
O6xi—Ca4—O6viii | 74.63 (12) | Ca2viii—O4—Ca2iv | 130.05 (13) |
O6iv—Ca4—O6viii | 74.63 (12) | Cr2—O5—Ca2 | 141.0 (2) |
O4ix—Ca4—Cr2xi | 87.33 (7) | Cr2—O5—Ca1vii | 93.62 (13) |
O4x—Ca4—Cr2xi | 82.61 (7) | Ca2—O5—Ca1vii | 101.66 (11) |
O4—Ca4—Cr2xi | 156.54 (9) | Cr2—O5—Ca1 | 90.08 (13) |
O6xi—Ca4—Cr2xi | 24.74 (7) | Ca2—O5—Ca1 | 110.41 (11) |
O6iv—Ca4—Cr2xi | 94.35 (8) | Ca1vii—O5—Ca1 | 122.56 (16) |
O6viii—Ca4—Cr2xi | 94.04 (8) | Cr2—O6—Ca4ii | 121.16 (16) |
O4ix—Ca4—Cr2iv | 82.61 (7) | Cr2—O6—Ca3ii | 100.86 (11) |
O4x—Ca4—Cr2iv | 156.54 (9) | Ca4ii—O6—Ca3ii | 99.97 (11) |
O4—Ca4—Cr2iv | 87.33 (7) | Cr2—O6—Ca3v | 103.06 (12) |
O6xi—Ca4—Cr2iv | 94.04 (8) | Ca4ii—O6—Ca3v | 98.81 (10) |
O6iv—Ca4—Cr2iv | 24.74 (7) | Ca3ii—O6—Ca3v | 135.61 (14) |
O6viii—Ca4—Cr2iv | 94.35 (7) | Cr2—O7—Ca1 | 97.99 (12) |
Cr2xi—Ca4—Cr2iv | 108.07 (3) | Cr2—O7—Ca2i | 121.14 (13) |
O4ix—Ca4—Cr2viii | 156.54 (9) | Ca1—O7—Ca2i | 111.84 (11) |
O4x—Ca4—Cr2viii | 87.33 (7) | Cr2—O7—Ca3ii | 90.88 (11) |
O4—Ca4—Cr2viii | 82.61 (7) | Ca1—O7—Ca3ii | 134.21 (11) |
O6xi—Ca4—Cr2viii | 94.35 (7) | Ca2i—O7—Ca3ii | 101.04 (10) |
O6iv—Ca4—Cr2viii | 94.04 (8) | Cr2—O8—Ca2v | 150.77 (16) |
O6viii—Ca4—Cr2viii | 24.74 (7) | Cr2—O8—Ca1vii | 96.75 (12) |
Cr2xi—Ca4—Cr2viii | 108.07 (3) | Ca2v—O8—Ca1vii | 111.10 (12) |
Cr2iv—Ca4—Cr2viii | 108.07 (3) | Cr2—O8—Ca3v | 89.29 (13) |
O4ix—Ca4—Cr1ix | 23.80 (7) | Ca2v—O8—Ca3v | 91.64 (10) |
O4x—Ca4—Cr1ix | 93.65 (8) | Ca1vii—O8—Ca3v | 105.39 (10) |
O4—Ca4—Cr1ix | 97.15 (8) | Cr3A—O9—Cr3B | 33.27 (14) |
O6xi—Ca4—Cr1ix | 85.90 (6) | Cr3A—O9—Ca3iii | 137.80 (19) |
O6iv—Ca4—Cr1ix | 85.01 (6) | Cr3B—O9—Ca3iii | 123.5 (2) |
O6viii—Ca4—Cr1ix | 154.81 (9) | Cr3A—O9—Ca2iii | 122.44 (17) |
Cr2xi—Ca4—Cr1ix | 72.538 (17) | Cr3B—O9—Ca2iii | 130.38 (18) |
Cr2iv—Ca4—Cr1ix | 70.851 (16) | Ca3iii—O9—Ca2iii | 98.63 (8) |
Cr2viii—Ca4—Cr1ix | 178.92 (3) |
Symmetry codes: (i) −x+y+2/3, y+1/3, z−1/6; (ii) −y+2/3, −x+1/3, z−1/6; (iii) −y, x−y, z; (iv) x+1/3, x−y−1/3, z+1/6; (v) x−1/3, x−y−2/3, z−1/6; (vi) −x+y+1/3, y−1/3, z+1/6; (vii) −x+y, −x, z; (viii) −y+1/3, −x+2/3, z+1/6; (ix) −y+1, x−y, z; (x) −x+y+1, −x+1, z; (xi) −x+y+4/3, y+2/3, z+1/6. |
Experimental details
Crystal data | |
Chemical formula | Ca10(CrO4)6(CrO4) |
Mr | 1212.80 |
Crystal system, space group | Trigonal, R3c |
Temperature (K) | 183 |
a, c (Å) | 10.7580 (1), 38.0730 (3) |
V (Å3) | 3816.02 (6) |
Z | 6 |
Radiation type | Mo Kα |
µ (mm−1) | 5.01 |
Crystal size (mm) | 0.09 × 0.08 × 0.08 |
Data collection | |
Diffractometer | Siemens SMART CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2003) |
Tmin, Tmax | 0.661, 0.690 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 13345, 2034, 1918 |
Rint | 0.036 |
(sin θ/λ)max (Å−1) | 0.667 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.024, 0.060, 1.04 |
No. of reflections | 2034 |
No. of parameters | 144 |
No. of restraints | 1 |
Δρmax, Δρmin (e Å−3) | 0.47, −0.66 |
Absolute structure | Flack (1983), 995 Friedel pairs |
Absolute structure parameter | 0.53 (3) |
Computer programs: SMART (Bruker, 2003), SAINT (Bruker, 2003) and SADABS (Sheldrick, 2003), SHELXTL (Sheldrick, 2008), DIAMOND (Brandenburg, 2012).
Ca1—O3i | 2.364 (3) | Ca3—O8iv | 2.865 (3) |
Ca1—O7 | 2.414 (3) | Ca4—O4ix | 2.284 (3) |
Ca1—O2ii | 2.502 (3) | Ca4—O4x | 2.284 (3) |
Ca1—O8iii | 2.537 (3) | Ca4—O4 | 2.284 (3) |
Ca1—O1i | 2.592 (3) | Ca4—O6xi | 2.307 (3) |
Ca1—O5iii | 2.609 (3) | Ca4—O6iv | 2.307 (3) |
Ca1—O5 | 2.646 (3) | Ca4—O6viii | 2.307 (3) |
Ca1—O3A | 2.753 (2) | Cr1—O1 | 1.671 (3) |
Ca2—O8iv | 2.339 (3) | Cr1—O2 | 1.675 (3) |
Ca2—O5 | 2.410 (3) | Cr1—O4 | 1.719 (3) |
Ca2—O4ii | 2.424 (3) | Cr1—O3 | 1.736 (3) |
Ca2—O4v | 2.437 (3) | Cr2—O8 | 1.673 (3) |
Ca2—O7vi | 2.442 (3) | Cr2—O5 | 1.693 (3) |
Ca2—O3v | 2.472 (3) | Cr2—O7 | 1.704 (3) |
Ca2—O9vii | 2.508 (3) | Cr2—O6 | 1.722 (3) |
Ca3—O1 | 2.400 (3) | Cr3A—Cr3B | 0.947 (4) |
Ca3—O2ii | 2.411 (3) | Cr3A—O3A | 1.666 (8) |
Ca3—O6viii | 2.413 (3) | Cr3A—O9 | 1.650 (2) |
Ca3—O9vii | 2.438 (3) | Cr3B—O3B | 1.547 (18) |
Ca3—O6iv | 2.453 (3) | Cr3B—O9 | 1.659 (3) |
Ca3—O7viii | 2.703 (3) | ||
O1—Cr1—O2 | 115.72 (15) | O5—Cr2—O7 | 105.20 (14) |
O1—Cr1—O3 | 102.52 (14) | O8—Cr2—O6 | 105.61 (15) |
O1—Cr1—O4 | 112.02 (15) | O5—Cr2—O6 | 115.04 (17) |
O2—Cr1—O3 | 121.04 (14) | O7—Cr2—O6 | 104.56 (13) |
O2—Cr1—O4 | 105.11 (14) | O3A—Cr3A—O9 | 106.09 (13) |
O4—Cr1—O3 | 99.38 (13) | O9—Cr3A—O9iii | 112.63 (11) |
O8—Cr2—O5 | 106.06 (15) | O3B—Cr3B—O9 | 107.2 (2) |
O8—Cr2—O7 | 120.89 (14) | O9—Cr3B—O9vii | 111.66 (18) |
Symmetry codes: (i) −x+y+2/3, y+1/3, z−1/6; (ii) −y+2/3, −x+1/3, z−1/6; (iii) −y, x−y, z; (iv) x+1/3, x−y−1/3, z+1/6; (v) x−1/3, x−y−2/3, z−1/6; (vi) −x+y+1/3, y−1/3, z+1/6; (vii) −x+y, −x, z; (viii) −y+1/3, −x+2/3, z+1/6; (ix) −y+1, x−y, z; (x) −x+y+1, −x+1, z; (xi) −x+y+4/3, y+2/3, z+1/6. |
In a reaction between magnesia-chrome brick from the refractory lining of rotary cement kilns and the raw material for portland cement clinkers, calcium chromates of various composition are formed. The reaction is deleterious to the lining, the quality of the product and possibly to the environment. For example, chromate compounds with empirical formulae Ca10Cr6O25, Ca3Cr2O8 and Ca5Cr3O12 form in oxidizing atmospheres at temperatures higher than 1173 K when the CaO:Cr2O3 molar ratio is larger than or equal to 3:1. These compounds have been extensively studied by the use of several techniques for the determination of the total chromium content and for the determination of chromium oxidation states, often average ones (Adendorff et al., 1992; Mirtič et al., 1992; Arčon et al., 1998). When heating takes place in the absence of oxygen, no calcium chromates will be formed (Ford et al., 1949).
The title compound has attracted interest as a significant phase in the CaO–CrOx system. Its formation reduces refractoriness of calcium-rich compositions of the system in an oxidizing atmosphere and represents a novel type of mixed-valence CrV/CrVI compound. The first preparation of a mixed-valence chromium compound from aqueous solution has been reported by Casari et al. (2006), namely NH4Cr(CrO4)2, which constituted a new structure type among the CrIII/CrVI ternary oxides.
The synthetists and suppliers of the crystals used in this study, Figusch & Pánek (1976), assumed the composition to be 9CaO.4CrO3.Cr2O3. The diffraction pattern and the values of the lattice parameters are very similar to those of Ca3(VO4)2 (Gopal & Calvo, 1973), Ca3(AsO4)2 (Gopal & Calvo, 1971) and β-Ca3(PO4)2 (Schroeder et al., 1977; Yashima et al., 2003), so that similarity/isomorphism of their crystal structures was assumed. The initial model of the structure was based on analogy with Ca3(VO4)2 (Gopal & Calvo, 1973), as the electron paramagnetic resonance (EPR) measurements (Plesch, 1979) confirmed the presence of CrV. In Ca3(VO4)2, one formula unit lies on the threefold axis, with one of the calcium-ion sites on this axis being half-occupied. Disregarding the Ca atom in the half-filled site, the displacement parameters of some atoms appeared to be anomalously high. These results suggest a variability in the environment of the Ca site depending on whether the site is empty or occupied. Problems occurring in analogous structures were encountered again, namely one of the calcium-ion sites on the threefold axis being half-occupied and the displacement parameters of an O atom on a threefold axis appearing to be anomalously high. Gopal & Calvo (1973) explained the higher values of the displacement parameters by positional disorder. The refinement of site occupancy factors resulted in a distinct decrease of the occupancies of these two atomic positions. This corresponds to a CaO deficit with regard to the chemical composition Ca3(VO4)2 (Gyepesová et al., 1981). The experimentally measured density was in good agreement with the calculated one either without 2.5 CaO or 3 Ca atoms in the hexagonal cell. Assuming that three Ca atoms are missing in the hexagonal cell, six of the Cr atoms must be hexavalent from the total of 42 Cr atoms. Taking this into account, another model (still not very satisfactory) for the title compound was presented (Gyepesová & Handlovič, 1980). Investigation of the electron structure of the title compound has also been performed using EPR methods and magnetic susceptibility measurements, which showed the presence of antiferromagnetism at low temperatures, and X-ray photoelectron spectroscopy methods, which indicated diferences in the oxidation states of the Cr atoms at the surface of the crystals (Stö\&ser et al., 1986).
The current determination of the title compound revealed that the crystal used was an almost ideal racemic twin. The atomic numbering scheme is shown in Fig. 1 and selected geometric parameters are given in Table 1. The CrO4 group on the threefold axis is disordered, with refined occupancies for Cr3A and Cr3B of 0.695 (6) and 0.305 (6), respectively, and with the same values applied to atoms O3A and O3B. The disordered CrO4 tetrahedra share three symmetry-related O9 atoms in a plane perpendicular to the c axis, as shown in Figs. 1 and 2. Significant differences in the Cr—O bond lengths in the CrO4 tetrahedra (Table 1) prove the presence of Cr in two oxidation states, viz. CrVI on the threefold axis (Cr3A and Cr3B) and CrV in general positions (Cr1 and Cr2), giving a final formula of Ca10(CrVO4)6(CrVIO4). The Ca atoms are coordinated by six, seven and eight O atoms, respectively, and the corresponding Ca—O distances for Ca1, Ca2 and Ca3 are in the ranges 2.364 (3)-2.753 (2), 2.339 (3)–2.508 (3) and 2.400 (3)–2.865 (3) Å, respectively. Atom Ca4 on the threefold axis is surrounded by six O atoms in an octahedral arrangement (Table 1 and Fig. 2). The projection of the structure along the a axis is shown in Fig. 3.
A comparison with β-Ca3(PO4)2 (Schroeder et al., 1977; Yashima et al., 2003) reveals that the expected close similarity/isomorphism of their crystal structures is not fully obvious, as the `half-filled Ca sites' for β-Ca3(PO4)2 are occupied in the title compound by the O atom on the threefold axis. Moreover, the title compound contains three fewer Ca atoms in the unit cell than β-Ca3(PO4)2. The O atom for the minor disorder component (O3B) is in the same position as in β-Ca3(PO4)2, but the fact that it does not have full site occupancy caused problems with the atomic displacement parameters for β-Ca3(PO4)2. The structure of the title compound can also be compared to Ca10K(PO4)7 (Sandström & Boström, 2006), which was obtained from a melt and is structurally related to β-Ca3(PO4)2 and presumably represents one end-member of a solid solution series. That structure contains four Ca, one K, three P and ten unique O atoms, of which the K, one Ca, one P and one O atom are located on threefold rotation axes. The K+ cation occupies a position equivalent to the `half-filled site' (Ca4) in the β-Ca3(PO4)2 structure.
Study of CaO sintering with the addition of Cr2O3 in air, where the title compound occurs (in the subsolidus area), shows an intensification of shrinkage, which may indicate increased grain boundary diffusion compared to pure CaO. The acceleration of this process depends on transport of Ca2+ ions (Figusch et al., 1979). From a stereochemical viewpoint, there are free spaces in the title compound in the vicinity of the threefold axes and their size is affected by the disorder of the O- and Cr-atom positions. In this way, a rapid transfer of Ca2+ ions across the free spaces can be assumed in the chemical potential gradient.