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Re-investigation and correct symmetry of Ca3CoAl4O10

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aUniversity of Innsbruck, Institute of Mineralogy & Petrography, Innrain 52, A-6020 Innsbruck, Austria
*Correspondence e-mail: volker.kahlenberg@uibk.ac.at

Edited by M. Weil, Vienna University of Technology, Austria (Received 24 December 2018; accepted 10 January 2019; online 15 January 2019)

A re-investigation of the crystal structure of tricalcium cobalt(II) tetra­aluminate, Ca3CoAl4O10, using single-crystal X-ray diffraction data, revealed ortho­rhom­bic (Pbcm) symmetry. The present contribution corrects the results of a previous X-ray powder diffraction study [Vazquez et al. (2002[Vazquez, B., Torres-Martinez, L. M., Alvarez, N., Vente, J. F. & Quintana, P. (2002). J. Solid State Chem. 166, 191-196.]). J. Solid State Chem. 166, 191–196] where this phase has been described in an unnecessarily low space-group symmetry (Pbc21). The compound belongs to the group of tetra­hedral framework structures. The distribution of the aluminium and cobalt ions among the centres of the four different tetra­hedra within the asymmetric unit has been studied in detail. Charge compensation is achieved by the incorporation of two symmetrically independent calcium ions located in voids of the tetra­hedral framework. Ca3CoAl4O10 is isotypic with Ca3MgAl4O10.

1. Chemical context

In a recent paper on the phase relationships in the system CaO–MgO–Al2O3, we reported the existence and the crystal structure of Ca3MgAl4O10 (Kahlenberg et al., 2018[Kahlenberg, V., Albrecht, R., Schmidmair, D., Krüger, H., Krüger, B., Tribus, M. & Pauluhn, A. (2018). https://doi. org/10.1111/jace. 16001]), a phase of inter­est for slags occurring in secondary refining processes in metallurgy or refractories, for example. In the course of this study it became obvious that the compound is closely related to the corresponding Zn and Co analogues that have already been reported in the literature (Barbanyagre et al., 1997[Barbanyagre, V. D., Timoshenko, T. I., Ilyinets, A. M. & Shamshurov, V. M. (1997). Powder Diffr. 12, 22-26.]; Vazquez et al., 2002[Vazquez, B., Torres-Martinez, L. M., Alvarez, N., Vente, J. F. & Quintana, P. (2002). J. Solid State Chem. 166, 191-196.]). In fact Vazquez et al. (2002[Vazquez, B., Torres-Martinez, L. M., Alvarez, N., Vente, J. F. & Quintana, P. (2002). J. Solid State Chem. 166, 191-196.]) used the coordinates from the Zn compound as a starting model for their Rietveld refinement of Ca3CoAl4O10. The major difference from our investigation on Ca3MgAl4O10 results from the fact that the previous study attributed Ca3CoAl4O10 to the acentric space group Pbc21, while Ca3MgAl4O10 crystallizes in the centrosymmetric space group Pbcm. However, for the former compound the description in an acentric space group has to be scrutinized. A detailed analysis of the atomic coordinates using the program PSEUDO (Kroumova et al., 2001[Kroumova, E., Aroyo, M. I., Perez-Mato, J. M., Ivantchev, S., Igartua, J. M. & Wondratschek, H. (2001). J. Appl. Cryst. 34, 783-784.]) indicated that the published model fulfills the symmetry requirements of Pbcm. Notably, Vazquez et al. (2002[Vazquez, B., Torres-Martinez, L. M., Alvarez, N., Vente, J. F. & Quintana, P. (2002). J. Solid State Chem. 166, 191-196.]) reported problems during their structure analysis of Ca3CoAl4O10, including unstable refinements and unrealistically short cation–oxygen distances. Both observations are typical features when a structure is refined in an unnecessarily low space-group symmetry (Baur & Tillmanns, 1986[Baur, W. H. & Tillmanns, E. (1986). Acta Cryst. B42, 95-111.]). Therefore, it was deemed appropriate to re-investigate the crystal structure of Ca3CoAl4O10 using single-crystal X-ray diffraction data obtained from melt-grown crystals.

2. Structural commentary

The crystal structure of Ca3CoAl4O10 can be described as a three-dimensional network with four symmetrically different corner-sharing [(Al,Co)O4] tetra­hedra around the central atoms T1–T4 (Fig. 1[link]). The basic building units of the structure are chains of tetra­hedra running parallel to [001]. Using the crystal chemical classification developed by Liebau (1985[Liebau, F. (1985). Structural Chemistry of Silicates, p. 347. Berlin, Heidelberg, New York, Tokyo: Springer.]), these linear elements can be described as mixed-branched vierer single chains (Fig. 2[link]). Condensation of adjacent chains along [010] results in the formation of stepped layers parallel to (100) (Fig. 3[link]). Within these layers, channels can be identified which host the additional calcium ions.

[Figure 1]
Figure 1
Projection of the crystal structure of Ca3CoAl4O10 in a view parallel to [100]. Displacement ellipsoids are shown at the 90% probability level. Colour codings for the atoms and polyhedra are as follows: blue: oxygen; red: aluminium/cobalt; Ca1: pink; Ca2: green; cobalt-containing tetra­hedra ([T1O4] and [T2O4]): lilac; pure aluminium tetra­hedra ([T3O4] and [T4O4]): grey.
[Figure 2]
Figure 2
A single mixed-branched vierer single chain (running parallel to [001]) representing the backbone of the framework in Ca3CoAl4O10. Displacement ellipsoids as in Fig. 1[link].
[Figure 3]
Figure 3
Projection of the crystal structure of Ca3CoAl4O10 in a view parallel to [001]. Displacement ellipsoids as in Fig. 1[link].

Site-occupancy refinements indicated that cobalt incorporation is limited to two of the four T sites within the asymmetric unit (T1 and T2). T3 and T4 are virtually cobalt free. The spread of the individual T—O bond lengths and the O—T—O angles follow expected crystallochemical trends. For the average T—O values, two groups can be distinguished: T1, T2: 1.808 Å and T3, T4: 1.758 Å. These values reflect the larger ionic radius of Co2+ for fourfold coordination [r(Co2+,[4]): 0.58 Å] when compared to the corresponding value for Al3+ [r(Al3+,[4]): 0.39 Å] (Shannon, 1976[Shannon, R. D. (1976). Acta Cryst. A32, 751-767.]), and can be used as an indication that T1 and T2 have higher Co contents. This observation compares well with the site-population refinements. Quadratic elongations as defined by Robinson et al. (1971[Robinson, K., Gibbs, G. V. & Ribbe, P. H. (1971). Science, 172, 567-570.]), which can be used as numerical descriptors for the distortions, take the following values for the individual [(Al,Co)O4]-groups: T1: 1.015, T2: 1.006, T3: 1.016, T4: 1.001.

Among the extra-framework cations, two crystallographically independent calcium sites (Ca1, Ca2) can be distinguished. They are coordinated by six and eight nearest oxygen neighbours. Their coordination polyhedra can be described as distorted octa­hedra and square anti­prisms, respectively. Each two [Ca1O6] octa­hedra and a single [Ca2O8] square anti­prism form a polyhedral unit by sharing edges.

A detailed analysis of the topological features of the tetra­hedral network including coordination sequences and extended point symbols has been already presented for isotypic Ca3MgAl4O10 (Kahlenberg et al., 2018[Kahlenberg, V., Albrecht, R., Schmidmair, D., Krüger, H., Krüger, B., Tribus, M. & Pauluhn, A. (2018). https://doi. org/10.1111/jace. 16001]) and will not be duplicated here. However, it is inter­esting to note that the framework consists of three (T3), four (T4) and five (T1, T2)-connected tetra­hedra. Notably, the net contains an O[3]-type bridging oxygen (O3), simultaneously linking three tetra­hedra (one [T2O4]- and two [T1O4]-units). In oxo-silicates that are based on [SiO4] units, for example, only terminal (O[1]) and simple bridging (O[2]) oxygen atoms have been observed so far. In the present structure, the oxygen atoms O1 and O2, O4, O5, O6, O7 belong to these two groups. Notably, O3 is solely involved in O—T bonds with the two tetra­hedra showing an Al/Co substitution.

3. Database survey

As mentioned above, the title compound is isotypic with Ca3MgAl4O10. For the calculation of several qu­anti­tative descriptors for the characterization of the degree of similarity between the crystal structures of Ca3CoAl4O10 and Ca3MgAl4O10, the program COMPSTRU (de la Flor et al., 2016[Flor, G. de la, Orobengoa, D., Tasci, E., Perez-Mato, J. M. & Aroyo, M. I. (2016). J. Appl. Cryst. 49, 653-664.]) was employed. For the given two structures, the degree of lattice distortion S, i.e. the spontaneous strain obtained from the eigenvalues of the finite Lagrangian strain tensor calculated in a Cartesian reference system, has a value of S = 0.0010. The structure of Ca3CoAl4O10 was transformed to the most similar configuration of Ca3MgAl4O10. The calculations revealed the following atomic displacements (in Å) between the corresponding atoms in Ca3CoAl4O10 and Ca3MgAl4O10: Ca1: 0.036; Ca2: 0.028; T1: 0.044; T2: 0.010; T3: 0.027; T4: 0.031; O1: 0.026; O2: 0.030; O3: 0.019; O4: 0.024; O5: 0.000; O6: 0.031; O7: 0.040, i.e. the maximum displacement is lower than 0.05 Å. The measure of similarity (Δ) as defined by Bergerhoff et al. (1999[Bergerhoff, G., Berndt, M., Brandenburg, K. & Degen, T. (1999). Acta Cryst. B55, 147-156.]) has a value of 0.007. Notably, for both structures the divalent cations Co2+ and Mg2+ are enriched in the tetra­hedral positions T1 and T2.

The distribution of the cobalt and aluminium ions on the different T sites is another difference between the new centrosymmetric model in Pbcm (this work) and the previous acentric model in Pbc21 (Vazquez et al., 2002[Vazquez, B., Torres-Martinez, L. M., Alvarez, N., Vente, J. F. & Quintana, P. (2002). J. Solid State Chem. 166, 191-196.]). Actually, in the latter case five different tetra­hedral positions have to be distinguished. The authors considered four of them to be exclusively occupied with Al while the remaining fifth position was attributed to be a pure cobalt site. This distribution, however, was derived from the crystal-structure refinement of the zinc analog (Barbanyagre et al., 1997[Barbanyagre, V. D., Timoshenko, T. I., Ilyinets, A. M. & Shamshurov, V. M. (1997). Powder Diffr. 12, 22-26.]) and not determined by site-occupancy refinements.

Furthermore, the new model in Pbcm results in considerably less distorted tetra­hedra. Although soft constraints on the Al—O and Co—O bond lengths had been applied, individual T—O distances and O—T—O angles in the Pbc21 structure model showed a pronounced variation between 1.68 and 2.05 Å and 92.9 and 124.6°, respectively. The corresponding values in the present model are in the ranges from 1.719 (4) to 1.847 (2) Å and from 98.95 (16) to 120.38 (18)°, respectively. Finally, the displacement parameters in Pbcm are all well behaved, while the overall isotropic temperature factor for the oxygen atoms reported in the study of Vazquez et al. (2002[Vazquez, B., Torres-Martinez, L. M., Alvarez, N., Vente, J. F. & Quintana, P. (2002). J. Solid State Chem. 166, 191-196.]) takes a physically unrealistic value of Uiso = 0.001 (2) Å2.

4. Synthesis and crystallization

Single crystals of Ca3CoAl4O10 were obtained during a series of synthesis experiments in the system CaO–CoO–Al2O3. 1.35 g of the educts consisting of CaCO3, CoO and Al2O3 in the molar ratio 14:6:5 were homogenized in an agate mortar, transferred into a platinum crucible and covered with a lid. The container was fired in a resistance-heated furnace from 590 to 1623 K with a ramp of 100 K h−1. The target temperature was held for 1 h. Subsequently, the sample was cooled down to 1273 K at a rate of 7.5 K h−1 and, finally, the temperature was reduced to 473 K at a rate of 100 K h−1. After removal of the crucible, the solidified melt cake was immediately crushed in an agate mortar and transferred to a glass slide under a polarizing binocular. A first inspection revealed the presence of two crystalline phases: larger colourless optically isotropic crystals of Ca3Al2O6 (up to 500 µm in size) and considerably smaller, intensively blue birefringent crystals of Ca3CoAl4O10. A platy fragment of the latter compound showing sharp extinction under crossed polarizers was selected for further structural studies and mounted on the tip of a glass fibre using fingernail hardener as glue.

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1[link]. Starting parameters for the atomic coordinates were taken from the crystal structure of Ca3Al4MgO10 (Kahlenberg et al., 2018[Kahlenberg, V., Albrecht, R., Schmidmair, D., Krüger, H., Krüger, B., Tribus, M. & Pauluhn, A. (2018). https://doi. org/10.1111/jace. 16001]). Initially, mixed cobalt–aluminium populations were considered for all four T sites. However, the resulting values of the site occupancies for T3 and T4 indicated pure Al populations (within two standard uncertainties each). In the final cycles a restraint was introduced, fixing the total amount of cobalt distributed among the remaining T1 and T2 sites to four atoms per unit cell.

Table 1
Experimental details

Crystal data
Chemical formula Al4Ca3CoO10
Mr 447.09
Crystal system, space group Orthorhombic, Pbcm
Temperature (K) 293
a, b, c (Å) 5.1324 (6), 16.7550 (19), 10.6822 (12)
V3) 918.60 (18)
Z 4
Radiation type Mo Kα
μ (mm−1) 3.97
Crystal size (mm) 0.12 × 0.09 × 0.06
 
Data collection
Diffractometer Rigaku Oxford Diffraction Xcalibur, Ruby, Gemini ultra
Absorption correction Analytical (CrysAlis PRO; Rigaku OD, 2015[Rigaku OD (2015). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]). Analytical numeric absorption correction using a multifaceted crystal model based on expressions published by Clark & Reid (1995[Clark, R. C. & Reid, J. S. (1995). Acta Cryst. A51, 887-897.]).
Tmin, Tmax 0.759, 0.898
No. of measured, independent and observed [I > 2σ(I)] reflections 5719, 973, 791
Rint 0.065
(sin θ/λ)max−1) 0.621
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.030, 0.061, 1.07
No. of reflections 973
No. of parameters 96
No. of restraints 1
Δρmax, Δρmin (e Å−3) 0.6, −0.64
Computer programs: CrysAlis PRO (Rigaku OD, 2015[Rigaku OD (2015). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]), SHELXL2017/1 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]), VESTA3 (Momma & Izumi, 2011[Momma, K. & Izumi, F. (2011). J. Appl. Cryst. 44, 1272-1276.]), publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]) and WinGX (Farrugia, 2012[Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849-854.]).

Supporting information


Computing details top

Data collection: CrysAlis PRO (Rigaku OD, 2015); cell refinement: CrysAlis PRO (Rigaku OD, 2015); data reduction: CrysAlis PRO (Rigaku OD, 2015); program(s) used to solve structure: coordinates from isotypic structure; program(s) used to refine structure: SHELXL2017/1 (Sheldrick, 2015); molecular graphics: VESTA3 (Momma & Izumi, 2011); software used to prepare material for publication: publCIF (Westrip, 2010) and WinGX (Farrugia, 2012).

Tricalcium cobalt(II) tetraaluminate top
Crystal data top
Ca3CoAl4O10F(000) = 876
Mr = 447.09Dx = 3.233 Mg m3
Orthorhombic, PbcmMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2c 2bCell parameters from 939 reflections
a = 5.1324 (6) Åθ = 5.0–28.4°
b = 16.7550 (19) ŵ = 3.97 mm1
c = 10.6822 (12) ÅT = 293 K
V = 918.60 (18) Å3Fragment, colourless
Z = 40.12 × 0.09 × 0.06 mm
Data collection top
Rigaku Oxford Diffraction Xcalibur, Ruby, Gemini ultra
diffractometer
973 independent reflections
Radiation source: fine-focus sealed X-ray tube, Enhance (Mo) X-ray Source791 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.065
Detector resolution: 10.3575 pixels mm-1θmax = 26.2°, θmin = 3.8°
ω scansh = 56
Absorption correction: analytical
(CrysAlisPro; Rigaku OD, 2015). Analytical numeric absorption correction using a multifaceted crystal model based on expressions published by Clark & Reid (1995).
k = 2015
Tmin = 0.759, Tmax = 0.898l = 1210
5719 measured reflections
Refinement top
Refinement on F21 restraint
Least-squares matrix: full w = 1/[σ2(Fo2) + (0.0197P)2 + 0.4838P]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.030(Δ/σ)max < 0.001
wR(F2) = 0.061Δρmax = 0.6 e Å3
S = 1.07Δρmin = 0.64 e Å3
973 reflectionsExtinction correction: SHELXL-2017/1 (Sheldrick 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
96 parametersExtinction coefficient: 0.0014 (4)
Special details top

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

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Al10.63528 (15)0.07769 (4)0.59968 (7)0.0076 (2)0.6196 (19)
Co10.63528 (15)0.07769 (4)0.59968 (7)0.0076 (2)0.3804 (19)
Al20.1321 (2)0.02939 (7)0.750.0068 (4)0.761 (4)
Co20.1321 (2)0.02939 (7)0.750.0068 (4)0.239 (4)
Al30.2463 (3)0.16550 (9)0.750.0043 (3)
Al40.3045 (3)0.250.50.0062 (4)
Ca10.80287 (14)0.10873 (4)0.57559 (7)0.0093 (2)
Ca20.7833 (2)0.20768 (6)0.250.0131 (3)
O10.5811 (6)0.1666 (2)0.750.0085 (8)
O20.0758 (7)0.0742 (2)0.750.0102 (8)
O30.4655 (8)0.0615 (2)0.750.0192 (10)
O40.1005 (5)0.21476 (14)0.6201 (2)0.0084 (6)
O50.500.50.0174 (9)
O60.4916 (5)0.17398 (15)0.5570 (2)0.0130 (6)
O70.0172 (5)0.07854 (19)0.8828 (2)0.0249 (7)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Al10.0068 (4)0.0079 (5)0.0082 (4)0.0011 (3)0.0006 (3)0.0001 (3)
Co10.0068 (4)0.0079 (5)0.0082 (4)0.0011 (3)0.0006 (3)0.0001 (3)
Al20.0072 (7)0.0052 (7)0.0080 (7)0.0001 (5)00
Co20.0072 (7)0.0052 (7)0.0080 (7)0.0001 (5)00
Al30.0042 (8)0.0054 (8)0.0034 (7)0.0015 (6)00
Al40.0072 (8)0.0058 (8)0.0056 (8)000.0003 (6)
Ca10.0080 (4)0.0119 (4)0.0080 (4)0.0004 (3)0.0010 (3)0.0005 (3)
Ca20.0116 (6)0.0077 (6)0.0200 (6)0.0011 (5)00
O10.0035 (19)0.013 (2)0.0085 (17)0.0022 (15)00
O20.009 (2)0.010 (2)0.0120 (18)0.0015 (15)00
O30.021 (2)0.026 (3)0.011 (2)0.0087 (19)00
O40.0083 (13)0.0085 (15)0.0083 (12)0.0018 (10)0.0007 (11)0.0021 (10)
O50.017 (2)0.017 (2)0.018 (2)0.0078 (17)0.0023 (18)0.0007 (17)
O60.0126 (15)0.0155 (16)0.0109 (13)0.0068 (12)0.0013 (11)0.0033 (11)
O70.0163 (16)0.043 (2)0.0152 (14)0.0090 (14)0.0037 (13)0.0088 (14)
Geometric parameters (Å, º) top
T1—O7i1.794 (3)T4—O4v1.758 (2)
T1—O51.8194 (7)Ca1—O6iv2.342 (3)
T1—O61.831 (3)Ca1—O12.389 (2)
T1—O31.847 (2)Ca1—O7vi2.389 (3)
T2—O21.759 (4)Ca1—O4vii2.391 (3)
T2—O31.794 (4)Ca1—O2vii2.402 (2)
T2—O71.810 (3)Ca1—O52.5273 (8)
T2—O7ii1.810 (3)Ca2—O1v2.348 (4)
T3—O11.719 (4)Ca2—O4viii2.503 (3)
T3—O21.762 (4)Ca2—O4ix2.503 (3)
T3—O4ii1.780 (3)Ca2—O6vi2.561 (3)
T3—O41.780 (3)Ca2—O6iv2.561 (3)
T4—O6iii1.758 (3)Ca2—O3iv2.762 (4)
T4—O6iv1.758 (3)Ca2—O7iv2.852 (3)
T4—O41.758 (2)Ca2—O7vi2.852 (3)
O7i—T1—O5116.51 (11)O2vii—Ca1—O5115.65 (9)
O7i—T1—O6114.80 (13)O1v—Ca2—O4viii79.73 (9)
O5—T1—O6109.33 (9)O1v—Ca2—O4ix79.73 (9)
O7i—T1—O3112.30 (14)O4viii—Ca2—O4ix67.34 (11)
O5—T1—O3102.92 (12)O1v—Ca2—O6vi87.38 (8)
O6—T1—O398.95 (16)O4viii—Ca2—O6vi156.79 (9)
O2—T2—O3116.90 (19)O4ix—Ca2—O6vi91.52 (8)
O2—T2—O7112.29 (13)O1v—Ca2—O6iv87.38 (8)
O3—T2—O7105.50 (13)O4viii—Ca2—O6iv91.52 (8)
O2—T2—O7ii112.29 (13)O4ix—Ca2—O6iv156.79 (9)
O3—T2—O7ii105.50 (13)O6vi—Ca2—O6iv107.20 (12)
O7—T2—O7ii103.2 (2)O1v—Ca2—O3iv126.24 (12)
O1—T3—O2120.38 (18)O4viii—Ca2—O3iv139.56 (7)
O1—T3—O4ii114.55 (12)O4ix—Ca2—O3iv139.56 (7)
O2—T3—O4ii101.18 (12)O6vi—Ca2—O3iv63.24 (7)
O1—T3—O4114.55 (12)O6iv—Ca2—O3iv63.24 (7)
O2—T3—O4101.18 (12)O1v—Ca2—O7iv150.06 (6)
O4ii—T3—O4102.48 (17)O4viii—Ca2—O7iv113.33 (9)
O6iii—T4—O6iv106.90 (19)O4ix—Ca2—O7iv81.05 (8)
O6iii—T4—O4110.19 (11)O6vi—Ca2—O7iv70.38 (8)
O6iv—T4—O4111.36 (12)O6iv—Ca2—O7iv117.70 (9)
O6iii—T4—O4v111.36 (12)O3iv—Ca2—O7iv61.43 (9)
O6iv—T4—O4v110.19 (11)O1v—Ca2—O7vi150.06 (6)
O4—T4—O4v106.90 (18)O4viii—Ca2—O7vi81.05 (8)
O6iv—Ca1—O188.56 (9)O4ix—Ca2—O7vi113.33 (9)
O6iv—Ca1—O7vi82.78 (10)O6vi—Ca2—O7vi117.70 (9)
O1—Ca1—O7vi167.86 (11)O6iv—Ca2—O7vi70.38 (8)
O6iv—Ca1—O4vii100.70 (9)O3iv—Ca2—O7vi61.43 (9)
O1—Ca1—O4vii81.24 (10)O7iv—Ca2—O7vi59.64 (11)
O7vi—Ca1—O4vii91.99 (9)T2—O2—T3140.8 (2)
O6iv—Ca1—O2vii163.33 (10)T2—O3—T1ii119.61 (11)
O1—Ca1—O2vii76.74 (10)T2—O3—T1119.61 (11)
O7vi—Ca1—O2vii110.44 (10)T1ii—O3—T1120.8 (2)
O4vii—Ca1—O2vii69.64 (11)T4—O4—T3118.32 (15)
O6iv—Ca1—O575.31 (7)T1—O5—T1iv180.00 (4)
O1—Ca1—O5104.40 (9)T4iv—O6—T1119.00 (15)
O7vi—Ca1—O581.67 (7)T1x—O7—T2119.94 (16)
O4vii—Ca1—O5172.84 (7)
Symmetry codes: (i) x+1, y, z+3/2; (ii) x, y, z+3/2; (iii) x+1, y+1/2, z; (iv) x+1, y, z+1; (v) x, y+1/2, z+1; (vi) x+1, y, z1/2; (vii) x+1, y, z; (viii) x+1, y+1/2, z+1; (ix) x+1, y+1/2, z1/2; (x) x1, y, z+3/2.
 

References

First citationBarbanyagre, V. D., Timoshenko, T. I., Ilyinets, A. M. & Shamshurov, V. M. (1997). Powder Diffr. 12, 22–26.  CrossRef CAS Google Scholar
First citationBaur, W. H. & Tillmanns, E. (1986). Acta Cryst. B42, 95–111.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationBergerhoff, G., Berndt, M., Brandenburg, K. & Degen, T. (1999). Acta Cryst. B55, 147–156.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationClark, R. C. & Reid, J. S. (1995). Acta Cryst. A51, 887–897.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationFarrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationFlor, G. de la, Orobengoa, D., Tasci, E., Perez-Mato, J. M. & Aroyo, M. I. (2016). J. Appl. Cryst. 49, 653–664.  Web of Science CrossRef IUCr Journals Google Scholar
First citationKahlenberg, V., Albrecht, R., Schmidmair, D., Krüger, H., Krüger, B., Tribus, M. & Pauluhn, A. (2018). https://doi. org/10.1111/jace. 16001  Google Scholar
First citationKroumova, E., Aroyo, M. I., Perez-Mato, J. M., Ivantchev, S., Igartua, J. M. & Wondratschek, H. (2001). J. Appl. Cryst. 34, 783–784.  CrossRef CAS IUCr Journals Google Scholar
First citationLiebau, F. (1985). Structural Chemistry of Silicates, p. 347. Berlin, Heidelberg, New York, Tokyo: Springer.  Google Scholar
First citationMomma, K. & Izumi, F. (2011). J. Appl. Cryst. 44, 1272–1276.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationRigaku OD (2015). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.  Google Scholar
First citationRobinson, K., Gibbs, G. V. & Ribbe, P. H. (1971). Science, 172, 567–570.  CrossRef PubMed CAS Web of Science Google Scholar
First citationShannon, R. D. (1976). Acta Cryst. A32, 751–767.  CrossRef CAS IUCr Journals Web of Science Google Scholar
First citationSheldrick, G. M. (2015). Acta Cryst. C71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar
First citationVazquez, B., Torres-Martinez, L. M., Alvarez, N., Vente, J. F. & Quintana, P. (2002). J. Solid State Chem. 166, 191–196.  CrossRef CAS Google Scholar
First citationWestrip, S. P. (2010). J. Appl. Cryst. 43, 920–925.  Web of Science CrossRef CAS IUCr Journals Google Scholar

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