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The structure of the thermoelectric lamellar misfit cobalt oxide [Ca2CoO3][CoO2]1.62 was refined again using single-crystal X-ray diffraction data. A new commensurate intrinsic modulation was observed involving a modulation vector orthogonal to the misfit direction (⅔,0,−⅓). The five-dimensional superspace group is C2/m(1δ0)(α0γ)gm and the structure was solved using a commensurate approximation. A new model is given involving an occupation modulation of the split sites of the [CoO] layer. This [CoO] layer can be described by triple chains running along b. The residual disorder along b can then be explained by the assumption of a local ordering with two types of clusters: CoO2 and Co5O4. A powder neutron diffraction experiment confirmed the ordering evidenced by the single-crystal X-ray diffraction study, but was not sufficient by itself to deal with this double modulated scheme. The new intrinsic modulation is destroyed by partial metal substitutions in the [CoO] layer. The structural modifications of this layer directly influence the physical properties which are related to the electronic structure of the [CoO2] layers.
Supporting information
(type here to add preparation details)
(type here to add refinement details)
Program(s) used to refine structure: Jana2000 (Petricek, Dusek & Palatinus, 2000); software used to prepare material for publication: Jana2000 (Petricek, Dusek & Palatinus, 2000).
Crystal data top
| Ca2Co2.496O6.117 | Z = 2 |
| Mr = 325.1 | F(000) = 313 |
| Monoclinic, X2/m† | Dx = 4.557 Mg m−3 |
| q1 = 0.66666a* + -0.33333c*; q2 = 1.62500b*‡ | Mo Kα radiation, λ = 0.71069 Å |
| a = 4.8395 Å | µ = 10.80 mm−1 |
| b = 4.5531 Å | T = 300 K |
| c = 10.8583 Å | Plate |
| β = 98.124° | 0.20 × 0.15 × 0.03 mm |
| V = 236.86 Å3 | |
† Symmetry operations: (1) x1, x2, x3, x4, x5; (2) −x1, x2, −x3, −x4, 1/2+x5; (3) −x1, −x2, −x3, −x4, −x5; (4) x1, −x2, x3, x4, 1/2−x5; (5) 1/2+x1, 1/2+x2, x3, x4, 1/2+x5; (6) 1/2−x1, 1/2+x2, −x3, −x4, x5; (7) 1/2−x1, 1/2−x2, −x3, −x4, 1/2−x5; (8) 1/2+x1, 1/2−x2, x3, x4, −x5.
‡  ; 
|
Data collection top
Bruker Kappa CCD
diffractometer | θmax = 45.0°, θmin = 5.8° |
| 4288 measured reflections | h = −9→9 |
| 2492 independent reflections | k = 0→9 |
| 1673 reflections with I > 3σ(I) | l = 0→21 |
| Rint = 0.005 | |
Refinement top
| Refinement on F | 78 parameters |
| R[F2 > 2σ(F2)] = 0.033 | Weighting scheme based on measured s.u.'s w = 1/σ2(F) |
| wR(F2) = 0.032 | (Δ/σ)max = 0.016 |
| S = 1.66 | Δρmax = 0.67 e Å−3 |
| 2492 reflections | Δρmin = −0.71 e Å−3 |
Crystal data top
| Ca2Co2.496O6.117 | β = 98.124° |
| Mr = 325.1 | V = 236.86 Å3 |
| Monoclinic, X2/m† | Z = 2 |
| q1 = 0.66666a* + -0.33333c*; q2 = 1.62500b*‡ | Mo Kα radiation |
| a = 4.8395 Å | µ = 10.80 mm−1 |
| b = 4.5531 Å | T = 300 K |
| c = 10.8583 Å | 0.20 × 0.15 × 0.03 mm |
† Symmetry operations: (1) x1, x2, x3, x4, x5; (2) −x1, x2, −x3, −x4, 1/2+x5; (3) −x1, −x2, −x3, −x4, −x5; (4) x1, −x2, x3, x4, 1/2−x5; (5) 1/2+x1, 1/2+x2, x3, x4, 1/2+x5; (6) 1/2−x1, 1/2+x2, −x3, −x4, x5; (7) 1/2−x1, 1/2−x2, −x3, −x4, 1/2−x5; (8) 1/2+x1, 1/2−x2, x3, x4, −x5.
‡  ; 
|
Data collection top
Bruker Kappa CCD
diffractometer | 1673 reflections with I > 3σ(I) |
| 4288 measured reflections | Rint = 0.005 |
| 2492 independent reflections | |
Refinement top
| R[F2 > 2σ(F2)] = 0.033 | 78 parameters |
| wR(F2) = 0.032 | Δρmax = 0.67 e Å−3 |
| S = 1.66 | Δρmin = −0.71 e Å−3 |
| 2492 reflections | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top| | x | y | z | Uiso*/Ueq | Occ. (<1) |
| Ca | 0.43009 (6) | 0 | 0.27488 (3) | 0.00852 (6) | |
| O1 | 0.0527 (2) | 0 | 0.66413 (10) | 0.0109 (2) | |
| Co1a | 0 | 0 | 0.5 | 0.0039 (4)* | 0.279 (5) |
| Co1b | 0.0766 (7) | 0.0666 (8) | 0.5 | 0.0044 (2)* | 0.1685 (14) |
| O2a | 0.1072 (19) | 0.5 | 0.4996 (4) | 0.0099 (14)* | 0.268 (10) |
| O2b | 0 | 0.421 (2) | 0.5 | 0.0080 (15)* | 0.205 (8) |
| Co2 | 0.75 | 0.75 | 0 | 0.00315 (4) | 0.9498 |
| O3 | 0.38597 (15) | 0.75 | −0.09328 (7) | 0.00587 (14) | 0.9757 |
Atomic displacement parameters (Å2) top| | U11 | U22 | U33 | U12 | U13 | U23 |
| Ca | 0.00730 (10) | 0.00866 (12) | 0.00953 (10) | 0 | 0.00093 (8) | 0 |
| O1 | 0.0109 (4) | 0.0109 (5) | 0.0109 (4) | 0 | 0.0011 (3) | 0 |
| Co2 | 0.00219 (6) | 0.00285 (7) | 0.00444 (7) | 0 | 0.00057 (5) | 0 |
| O3 | 0.0047 (2) | 0.0054 (3) | 0.0076 (3) | 0 | 0.00127 (19) | 0 |
Geometric parameters (Å, º) top| | Average | Minimum | Maximum |
| Co2—O3 | 1.9040 (12) | 1.9028 (17) | 1.9053 (18) |
| Co2—O3i | 1.9003 (9) | 1.8868 (6) | 1.9142 (6) |
| Co2—O3ii | 1.9003 (9) | 1.8868 (6) | 1.9142 (6) |
| Co2—O31iii | 1.9003 (6) | 1.8866 (6) | 1.9143 (6) |
| Co2—O31 | 1.9003 (6) | 1.8866 (6) | 1.9143 (6) |
| Co2—O31iv | 1.9040 (7) | 1.9028 (8) | 1.9053 (8) |
| | | |
| O3—Co2—O3i | 85.37 (4) | 84.11 (3) | 86.65 (3) |
| O3—Co2—O3ii | 85.37 (4) | 84.11 (3) | 86.65 (3) |
| O3—Co2—O31iii | 94.62 (4) | 93.02 (3) | 96.26 (3) |
| O3—Co2—O31 | 94.62 (4) | 93.02 (3) | 96.26 (3) |
| O3—Co2—O31iv | 179.43 (5) | 179.11 (7) | 179.89 (3) |
| O3i—Co2—O3 | 85.37 (4) | 84.11 (3) | 86.65 (4) |
| O3i—Co2—O3ii | 95.02 (4) | 94.17 (3) | 95.86 (3) |
| O3i—Co2—O31iii | 84.97 (3) | 84.95 (3) | 84.99 (4) |
| O3i—Co2—O31 | 178.73 (4) | 178.01 (4) | 179.76 (5) |
| O3i—Co2—O31iv | 94.62 (4) | 93.00 (3) | 96.23 (3) |
| O3ii—Co2—O3 | 85.37 (4) | 84.11 (3) | 86.65 (4) |
| O3ii—Co2—O3i | 95.02 (4) | 94.17 (3) | 95.86 (3) |
| O3ii—Co2—O31iii | 178.73 (4) | 178.01 (4) | 179.76 (5) |
| O3ii—Co2—O31 | 84.97 (3) | 84.95 (3) | 84.99 (4) |
| O3ii—Co2—O31iv | 94.62 (4) | 93.00 (3) | 96.23 (3) |
| O31iii—Co2—O31 | 95.02 (3) | 94.14 (3) | 95.84 (3) |
| O31iii—Co2—O31iv | 85.37 (3) | 84.10 (3) | 86.63 (3) |
| O31—Co2—O31iii | 95.02 (3) | 94.14 (3) | 95.84 (3) |
| O31—Co2—O31iv | 85.37 (3) | 84.10 (3) | 86.63 (3) |
| O31iv—Co2—O31iii | 85.37 (3) | 84.10 (3) | 86.63 (3) |
| O31iv—Co2—O31 | 85.37 (3) | 84.10 (3) | 86.63 (3) |
| Symmetry codes: (i) −x1+1, −x2+1, −x3, −x4, −x5; (ii) −x1+1, −x2+2, −x3, −x4, −x5; (iii) x1, x2−1, x3, x4, x5; (iv) −x1+2, −x2+2, −x3, −x4, −x5. |
Experimental details
| Crystal data |
| Chemical formula | Ca2Co2.496O6.117 |
| Mr | 325.1 |
| Crystal system, space group | Monoclinic, X2/m† |
| Temperature (K) | 300 |
| Wave vectors | q1 = 0.66666a* + -0.33333c*; q2 = 1.62500b*‡ |
| a, b, c (Å) | 4.8395, 4.5531, 10.8583 |
| β (°) | 98.124 |
| V (Å3) | 236.86 |
| Z | 2 |
| Radiation type | Mo Kα |
| µ (mm−1) | 10.80 |
| Crystal size (mm) | 0.20 × 0.15 × 0.03 |
| |
| Data collection |
| Diffractometer | Bruker Kappa CCD
diffractometer |
| Absorption correction | – |
No. of measured, independent and
observed [I > 3σ(I)] reflections | 4288, 2492, 1673 |
| Rint | 0.005 |
| (sin θ/λ)max (Å−1) | 0.995 |
| |
| Refinement |
| R[F2 > 2σ(F2)], wR(F2), S | 0.033, 0.032, 1.66 |
| No. of reflections | 2492 |
| No. of parameters | 78 |
| No. of restraints | ? |
| Δρmax, Δρmin (e Å−3) | 0.67, −0.71 |
Selected geometric parameters (Å, º) top| | Average | Minimum | Maximum |
| Co2—O3 | 1.9040 (12) | 1.9028 (17) | 1.9053 (18) |
| Co2—O3i | 1.9003 (9) | 1.8868 (6) | 1.9142 (6) |
| Co2—O3ii | 1.9003 (9) | 1.8868 (6) | 1.9142 (6) |
| Co2—O31iii | 1.9003 (6) | 1.8866 (6) | 1.9143 (6) |
| Co2—O31 | 1.9003 (6) | 1.8866 (6) | 1.9143 (6) |
| Co2—O31iv | 1.9040 (7) | 1.9028 (8) | 1.9053 (8) |
| | | |
| O3—Co2—O3i | 85.37 (4) | 84.11 (3) | 86.65 (3) |
| O3—Co2—O3ii | 85.37 (4) | 84.11 (3) | 86.65 (3) |
| O3—Co2—O31iii | 94.62 (4) | 93.02 (3) | 96.26 (3) |
| O3—Co2—O31 | 94.62 (4) | 93.02 (3) | 96.26 (3) |
| O3—Co2—O31iv | 179.43 (5) | 179.11 (7) | 179.89 (3) |
| O3i—Co2—O3 | 85.37 (4) | 84.11 (3) | 86.65 (4) |
| O3i—Co2—O3ii | 95.02 (4) | 94.17 (3) | 95.86 (3) |
| O3i—Co2—O31iii | 84.97 (3) | 84.95 (3) | 84.99 (4) |
| O3i—Co2—O31 | 178.73 (4) | 178.01 (4) | 179.76 (5) |
| O3i—Co2—O31iv | 94.62 (4) | 93.00 (3) | 96.23 (3) |
| O3ii—Co2—O3 | 85.37 (4) | 84.11 (3) | 86.65 (4) |
| O3ii—Co2—O3i | 95.02 (4) | 94.17 (3) | 95.86 (3) |
| O3ii—Co2—O31iii | 178.73 (4) | 178.01 (4) | 179.76 (5) |
| O3ii—Co2—O31 | 84.97 (3) | 84.95 (3) | 84.99 (4) |
| O3ii—Co2—O31iv | 94.62 (4) | 93.00 (3) | 96.23 (3) |
| O31iii—Co2—O31 | 95.02 (3) | 94.14 (3) | 95.84 (3) |
| O31iii—Co2—O31iv | 85.37 (3) | 84.10 (3) | 86.63 (3) |
| O31—Co2—O31iii | 95.02 (3) | 94.14 (3) | 95.84 (3) |
| O31—Co2—O31iv | 85.37 (3) | 84.10 (3) | 86.63 (3) |
| O31iv—Co2—O31iii | 85.37 (3) | 84.10 (3) | 86.63 (3) |
| O31iv—Co2—O31 | 85.37 (3) | 84.10 (3) | 86.63 (3) |
| Symmetry codes: (i) −x1+1, −x2+1, −x3, −x4, −x5; (ii) −x1+1, −x2+2, −x3, −x4, −x5; (iii) x1, x2−1, x3, x4, x5; (iv) −x1+2, −x2+2, −x3, −x4, −x5. |
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