NaCa₄Nb₅O₁₇: a layered perovskite A_nB_nO_3n+2 compound

Sodium tetracalcium pentaniobium heptadecaoxide, NaCa₄­Nb₅O₁₇, corresponds to the n = 5 term of the homologous A_nB_nO_3n+2 family of structures composed of ABX₃ perovskite layers. The structure consists of perovskite-type blocks of n = 5 layers of NbO₆ octahedra, separated by an interblock region. Successive blocks along the b axis are displaced by c with respect to each other. The deformation of the NbO₆ octahedra is a minimum at the middle of each block, and increases along the direction of the b axis to a maximum at each end of the block. Ca and Na share the same intrablock sites, coordinated by 12 O atoms, whereas only Ca atoms are found in the interblock cavities, at sites with different coordination geometries.

S1. Comment

Compounds of the series A_nB_nO_3n+2 (where A is Ca, La or Sr, and B is Ti or Nb) with n = 4, 4.5, 5, 6 and 7 have attracted attention because of their interesting physical properties and their flexibility in accommodating various compositions (Lichtenberg et al., 2001). The structure of these compounds is derived from the ABX₃ perovskite, in which BX₆ octahedra share corners and A cations lie in the X cavities. For any value of n, the ideal structure of the corresponding compound can be interpreted in terms of blocks formed by BO₆ octahedra, which blocks are stacked along the [110]p direction of the ideal perovskite structure. The periodicity along the stacking direction (conventionally labelled as the b axis) contains two blocks of n octahedral layers, so that its magnitude depends on the composition and is, to a first approximation, given by b ≈ (n+1)2^1/2a_p (a_p = 3.933 Å; Levin & Bendersky, 1999). The other two cell vectors, usually defined as a = [100]p (a = 3.93 Å) and c = [011]p (c = 5.6 Å), span the (011)p blocks of octahedra. This setting of the orthorhombic cell parameters is generally used for the structural description of the family. Consecutive blocks of octahedra are shifted with respect to each other by the vector 1/2(a+c), leaving interlayer regions where octahedra do not share two O atoms. Note that the ideal perovskite structure corresponds to the limiting value n = ∞, i.e. with a single infinitely thick slab of octahedra. On the other hand, n = 4 is the lower limit, due to valence considerations. Intermediate integral values of n correspond to equally thick sequences of blocks, but non-integer values are also possible and correspond to sequences of octahedra-based blocks with alternating numbers of layers, e.g. n = 4.5 corresponds to alternating blocks of four and five layers.

A general description and symmetry classification of this type of structure has been reported by Levin & Bendersky (1999). Based on the tilts of the octahedra (Glazer, 1972), they present a scheme relating the stacking sequence and octahedral tilts to the symmetry of A_nB_nO_3n+2 structures. The review contains references to 40 compounds, six of which correspond to compositions with n = 5. More recently, Levin et al. (2000) published a transmission electron microscopy study of the Sr_n(Nb,Ti)_nO_3n+2 series, with n = 4, 4.5, 5, 6 and 7. They reported the existence of commensurate → incommensurate phase transitions for members with n = 4, 5, 6 and 7, with modulation vectors close to 1/2a*. A lock-in phase to 1/2a* was only confirmed for the compound with n = 5. However, phases with a cell parameter a ≈ 2a_p (7.7 Å) are very common, as reported in the review by Lichtenberg et al. (2001), and result from the presence of an alternating tilt of the octahedra around the b axis.

A different approach for describing this family of compounds has been proposed by Elcoro et al. (2001). Based on the superspace formalism, they describe many known phases of the Sr_n(Nb,Ti)_nO_3n+2 series as modulated structures, with a composition-dependent primary modulation wavevector q = γb* [γ = 1/(1+n)] and step-like occupational modulation functions. In this way, the introduction of the composition variable n within the `structural parameter' q leads to a unique structural model with a unique superspace group. The efficacy of this method was tested by comparing the symmetry reported for members of this family with the resulting space groups derived from the superspace model; even the case of symmetry breaking due to the phase transitions present in many compounds can be taken into account with this method.

With the aim of testing the superspace method described above, we have prepared new compounds of the A_nB_nO_3n+2 family. In this paper, we report the structure of a system with mixed Ca/Na composition for the A cations and with B = Nb. The first studies on Ca-based compounds of this series were carried out by Nanot et al. (1979, 1981, 1986). For the compounds (La₄Ca)Ti₅O₁₇, (Nb₄Ca)Ti₅O₁₇ and Ca₅(Nb₄Ti)O₁₇, despite the apparent orthorhombic symmetry (C222₁) observed on precession photographs, they proposed a monoclinic cell with similar a and c axes, but with b' = 1/2(b-a) and with P2₁/b or P2₁ as possible space groups; the apparent orthorhombic symmetry was attributed to systematic pseudo-merohedral twinning of the crystals. For all three compounds, a cell parameter a = 2a_p was reported. In the present case, NaCa₄Nb₅O₁₇, we confirm a monoclinic cell and P2₁/b as space group.

A projection of the structure of NaCa₄Nb₅O₁₇ is shown in Figs. 1a and 1 b. Owing to the monoclinic distortion, successive slabs of octahedra stacked along the b axis direction are shifted by 1/2c. The shift transforms to 1/2(a+c) when the parameters of the C-centred orthorhombic cell are used. Thus, the packing of the blocks does in fact correspond to that expected for a structural motif composed of an odd number of layers of octahedra. Similar packing is found in Sr₅TiNb₄O₁₇ (Drews et al., 1996) and Sr₅Nb₅O₁₇ (Schmalle et al., 1995). The structure has a pseudo lattice translation of (1/2)a for the heavy atoms, which is broken by differing tilts of the oxygen octahedra; successive octahedra along the a axis exhibit tilts around b in antiphase; that is, consecutive octahedra along the a axis are successively tilted clockwise and anticlockwise. This fact, and the weakness of the superlattice reflections with k = 2n, permits a description of this phase as a modulation with wavevector q = (1/2)a* (lock-in phase) of a hypothetical higher-temperature phase (incommensurate phase). Such a phase transition has been reported for other compounds (Levin at al., 2000) experiencing the sequence of symmetries Immm → Pmnn → Inc → P112₁/b, with the final structure being associated with an a⁺b or a⁺c tilt of the untilted high-temperature Immm structure.

The distorted octahedra in NaCa₄Nb₅O₁₇ have Nb—O distances within two different ranges. The shortest and longest distances for octahedra in the middle of the block (Nb1 and Nb2) range from 1.965 (2) to 1.990 (2) Å, for the next layer of octahedra outward from the centre the distances range from 1.843 (2) to 2.164 (2) Å, and for the octahedra at the edges of the blocks the distances range from 1.798 (2) to 2.259 (2) Å. Thus the distortion of the octahedra clearly increases from the centres to the edges of the slabs. The Ca atoms located in the O-bounded cavities between octahedra are arranged in columns along the a axis and exhibit two different coordination environments. Atoms Ca1 and Ca2 are in the inter-block region, in sites fully occupied by Ca; Ca1 is coordinated to 7 O atoms, with distances ranging from 2.303 (2) to 2.529 (2) Å, and Ca2 is coordinated to 6 + 3 O atoms, at distances in the range 2.398 (2)–3.277 (2) Å with a break at 2.643 (2) Å. Atoms Ca3, Ca4 and Ca5, embedded in the blocks, are 12-coordinate, with Ca—O distances ranging from 2.343 (2) to 3.348 (2) Å.

The refinement of the occupancy factors of the Ca/Na atoms shows that the Na atoms are located inside the slabs. This preference is in accord with the charge distribution in the structure. The interslab regions have an excess of O atoms and so full occupancy of Ca favours local electroneutrality. A random distribution of the Na atoms at the sites inside the slabs would correspond to occupancy factors of 2/3 and 1/3 for Ca and Na, respectively. But, according to the refined values, the Ca sites in the middle of the blocks (Ca3 type) have a higher proportion of Ca [0.747 (3)], while those closer to the edges have Ca fractions of 0.796 (4) (Ca4) and 0.457 (4) (Ca5). A similar distribution has been reported for Nd₄Ca₂Ti₆O₂₀ (Nanot et al., 1976), in which Ca atoms replace Nd preferentially on sites away from the interblock regions.

S2. Experimental

Single crystals of NaCa₄Nb₅O₁₇ were isolated by heating a mixture corresponding to the composition Na₂Ca₄Nb₆O₂₀, under oxygen at 1753 K. Na₂Ca₄Nb₆O₂₀ was initially prepared by firing the appropriate stoichiometric mixture of Na₂CO₃, CaCO₃ and Nb₂O₅. The sample was mixed in an agate mortar and heated in an alumina crucible at 1223 K for 24 h, and in a final step at 1473 K for 24 h. The preparations were carried out under a flow of oxygen.

S3. Refinement

The diffraction patterns from precession photographs show weak (hkl) h = 2n+1 layers and an apparent orthorhombic symmetry. With reference to the orthorhombic cell (a = 7.710, b = 64.24 and c = 5.4838 Å), the systematic absences observed were those of C-centring including k = 2n+1 for (0k0). Such a lattice type has been registered for compounds with n = 4 and 6, but the tilt pattern expected in the present case, with an odd number of octahedra-based layers per block, points to a P-type orthorhombic or monoclinic space group (Levin & Bendersky, 1999). However, attempts to find a solution in the space group C222₁ failed. Using the direct methods routines of SHELXS97 (Sheldrick, 1997), a solution was found and refined in both P2₁ and P2₁/b, with the lattice constants given in the crystal data table (an unconventional setting is used to permit facile comparisons with other, previously published work). The choice of this monoclinic cell assumes a pseudo-merohedral twinned crystal with perfect superposition of both lattices (note that the monoclinic angle is almost 90° in the C-centred cell), and a twin law given by a binary axis about the [100] direct lattice direction, relating (hkl) and (h,-(h+k),-l) reflection pairs from each twin. The violation of the systematic absences for the b-glide plane were assumed to be due to the twinning, so the centrosymmetric space group was chosen. In fact, only reflections of type (hk0) h = odd and k = odd were observed to violate the b-glide extinctions and correspond to reflections (odd,even,0) of the second twin component. Using the twin model and with all A sites fully occupied by Ca atoms, the refinement converged to R = 0.057 (all atoms anisotropic); at this point, some Ca atoms showed large atomic displacements. A model containing Na and Ca atoms was employed, constraining the population factors to the given composition and keeping the anisotropic displacements equal for all Ca/Na sites during the refinement. Near the end of the refinement, the occupancy factors for the Ca atoms in the interlayer regions were close to 1 and they were fixed to that value in the final cycles. The final population parameter for the twin was 0.5559 (9).

Computing details

Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: STRUPLO84 (Fischer, 1985).

Figures

Fig. 1. Projections of the structure of NaCa4Nb5O17 along (a) the [001] and (b) the [100] direction.

(I)

Crystal data

Ca4NaNb5O17	F(000) = 1728
Mr = 919.82	Dx = 4.499 Mg m^−3
Monoclinic, P1121/b	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: -P 2bc	Cell parameters from 25 reflections
a = 7.710 (2) Å	θ = 9.1–29.6°
b = 32.350 (5) Å	µ = 5.74 mm^−1
c = 5.4838 (6) Å	T = 293 K
β = 90°	Parallelepiped, colourless
V = 1358.0 (4) Å^3	0.21 × 0.08 × 0.05 mm
Z = 4

Data collection

Enraf-Nonius CAD-4 diffractometer	Rint = 0.035
non–profiled ω/2θ scans	θmax = 40.0°, θmin = 1.9°
Absorption correction: gaussian [PLATON (Spek, 1990) and WinGX (Farrugia, 1999)]	h = −13→13
Tmin = 0.599, Tmax = 0.759	k = −58→58
17947 measured reflections	l = 0→9
8692 independent reflections	3 standard reflections every 60 min
6585 reflections with I > 2σ(I)	intensity decay: none

Refinement

Refinement on F^2	1 restraint
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + (0.0289P)^2 + 1.0534P] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.028	(Δ/σ)max = 0.032
wR(F^2) = 0.071	Δρmax = 2.12 [at (0.5188,0.0165,0.0006), 0.54Å from Nb02] e Å^−3
S = 1.06	Δρmin = −2.23 [at (−0.0029,0.000,0.8794), 0.66Å from Nb01] e Å^−3
8692 reflections	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
252 parameters	Extinction coefficient: 0.00168 (6)

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Nb1	0.0	0.5	0.5	0.00471 (4)
Nb2	0.5	0.5	0.5	0.00484 (4)
Nb3	0.04653 (5)	0.590626 (6)	0.00067 (4)	0.00465 (3)
Nb4	0.54524 (5)	0.591230 (5)	−0.00065 (4)	0.00472 (3)
Nb5	0.08743 (5)	0.677064 (6)	0.51853 (4)	0.00484 (3)
Nb6	0.59507 (5)	0.677922 (6)	0.52199 (4)	0.00481 (4)
Ca1	0.86245 (8)	0.721758 (14)	0.07847 (8)	0.00756 (7)
Ca2	0.36211 (9)	0.708872 (17)	0.00755 (9)	0.01337 (8)
Ca3	0.25409 (8)	0.505615 (15)	0.00672 (11)	0.00775 (10)	0.747 (3)
Ca4	0.29892 (10)	0.594439 (15)	0.49543 (9)	0.00737 (11)	0.796 (4)
Ca5	0.79183 (15)	0.58280 (2)	0.50277 (13)	0.01099 (16)	0.457 (4)
Na3	0.25409 (8)	0.505615 (15)	0.00672 (11)	0.00775 (10)	0.253 (3)
Na4	0.29892 (10)	0.594439 (15)	0.49543 (9)	0.00737 (11)	0.204 (4)
Na5	0.79183 (15)	0.58280 (2)	0.50277 (13)	0.01099 (16)	0.543 (4)
O1	0.2470 (3)	0.49542 (5)	0.5794 (3)	0.0087 (3)
O2	−0.0183 (2)	0.53477 (6)	0.7908 (4)	0.0089 (4)
O3	0.0687 (2)	0.54949 (6)	0.2923 (4)	0.0085 (3)
O4	0.4819 (3)	0.54977 (6)	0.2927 (4)	0.0088 (3)
O5	0.5528 (3)	0.53465 (6)	0.7911 (4)	0.0095 (4)
O6	0.7926 (3)	0.58549 (6)	0.0716 (3)	0.0104 (3)
O7	0.2891 (3)	0.57907 (5)	−0.0781 (3)	0.0062 (2)
O8	0.0327 (2)	0.61919 (6)	0.7006 (3)	0.0075 (4)
O9	0.1189 (3)	0.63377 (7)	0.2103 (4)	0.0095 (3)
O10	0.5160 (2)	0.63518 (6)	0.2051 (4)	0.0091 (3)
O11	0.5848 (3)	0.61792 (6)	0.6952 (3)	0.0075 (4)
O12	0.8355 (3)	0.66952 (5)	0.4234 (3)	0.0086 (3)
O13	0.3353 (3)	0.66849 (5)	0.5878 (3)	0.0081 (2)
O14	0.0786 (3)	0.71089 (6)	0.7871 (4)	0.0087 (3)
O15	0.1378 (2)	0.71939 (6)	0.2962 (4)	0.0073 (3)
O16	0.5907 (3)	0.72361 (6)	0.3153 (4)	0.0089 (4)
O17	0.6363 (2)	0.70373 (6)	0.8102 (4)	0.0098 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Nb1	0.00417 (10)	0.00565 (9)	0.00432 (9)	0.00065 (18)	0.00022 (18)	−0.00015 (9)
Nb2	0.00423 (10)	0.00591 (10)	0.00442 (9)	0.00080 (18)	0.00061 (18)	−0.00034 (9)
Nb3	0.00415 (8)	0.00473 (7)	0.00496 (7)	0.00006 (15)	0.00070 (12)	0.00002 (7)
Nb4	0.00408 (7)	0.00476 (7)	0.00518 (7)	−0.00007 (15)	0.00043 (12)	0.00010 (7)
Nb5	0.00429 (7)	0.00503 (7)	0.00517 (7)	0.00036 (13)	0.00034 (11)	0.00001 (6)
Nb6	0.00360 (7)	0.00552 (7)	0.00513 (7)	−0.00020 (12)	−0.00016 (11)	0.00011 (6)
Ca1	0.00636 (15)	0.00983 (16)	0.00648 (13)	0.00090 (19)	0.0003 (2)	0.00034 (12)
Ca2	0.00814 (18)	0.0232 (2)	0.00920 (16)	0.0037 (2)	0.0005 (2)	0.00124 (16)
Ca3	0.00720 (18)	0.0098 (2)	0.00636 (18)	0.00142 (19)	0.0010 (3)	0.00126 (17)
Ca4	0.00622 (19)	0.00963 (19)	0.00642 (18)	0.0016 (2)	0.0005 (3)	−0.00100 (14)
Ca5	0.0082 (3)	0.0165 (3)	0.0083 (3)	0.0017 (3)	0.0005 (4)	−0.0038 (2)
Na3	0.00720 (18)	0.0098 (2)	0.00636 (18)	0.00142 (19)	0.0010 (3)	0.00126 (17)
Na4	0.00622 (19)	0.00963 (19)	0.00642 (18)	0.0016 (2)	0.0005 (3)	−0.00100 (14)
Na5	0.0082 (3)	0.0165 (3)	0.0083 (3)	0.0017 (3)	0.0005 (4)	−0.0038 (2)
O1	0.0045 (6)	0.0121 (7)	0.0095 (6)	0.0013 (7)	0.0007 (7)	−0.0014 (5)
O2	0.0098 (9)	0.0088 (8)	0.0075 (7)	−0.0017 (6)	0.0033 (6)	−0.0028 (6)
O3	0.0096 (8)	0.0084 (9)	0.0072 (8)	−0.0003 (6)	0.0004 (6)	0.0017 (6)
O4	0.0104 (8)	0.0083 (9)	0.0083 (8)	0.0031 (6)	0.0023 (6)	0.0025 (7)
O5	0.0121 (9)	0.0091 (8)	0.0078 (7)	0.0038 (6)	−0.0023 (6)	−0.0028 (6)
O6	0.0045 (6)	0.0190 (8)	0.0079 (6)	0.0018 (8)	0.0015 (8)	−0.0004 (5)
O7	0.0031 (5)	0.0081 (6)	0.0076 (5)	0.0011 (7)	0.0001 (8)	0.0003 (5)
O8	0.0075 (10)	0.0075 (7)	0.0069 (7)	−0.0013 (6)	−0.0010 (6)	0.0028 (6)
O9	0.0096 (7)	0.0111 (9)	0.0081 (8)	0.0022 (6)	−0.0003 (6)	−0.0036 (7)
O10	0.0091 (7)	0.0088 (8)	0.0089 (8)	−0.0001 (6)	0.0008 (6)	−0.0036 (7)
O11	0.0083 (10)	0.0092 (7)	0.0053 (6)	0.0023 (6)	0.0013 (6)	0.0020 (6)
O12	0.0035 (5)	0.0128 (7)	0.0095 (6)	0.0016 (7)	−0.0005 (8)	−0.0008 (5)
O13	0.0037 (5)	0.0087 (6)	0.0123 (6)	0.0018 (7)	0.0006 (9)	0.0001 (5)
O14	0.0095 (9)	0.0107 (8)	0.0060 (7)	0.0016 (6)	0.0011 (6)	−0.0010 (5)
O15	0.0076 (9)	0.0070 (7)	0.0075 (7)	0.0014 (5)	0.0008 (6)	0.0015 (5)
O16	0.0095 (9)	0.0101 (8)	0.0074 (7)	0.0020 (6)	0.0009 (6)	0.0011 (5)
O17	0.0075 (8)	0.0148 (9)	0.0068 (7)	0.0002 (6)	−0.0010 (5)	−0.0041 (6)

Geometric parameters (Å, º)

Nb1—O2	1.966 (2)	Ca3—O4^viii	3.304 (2)
Nb1—O1	1.976 (2)	Ca3—O3^ix	3.318 (2)
Nb1—O3	1.9849 (19)	Ca4—O7^x	2.3904 (17)
Nb2—O5	1.965 (2)	Ca4—O4	2.408 (2)
Nb2—O1	1.987 (2)	Ca4—O3	2.427 (2)
Nb2—O4	1.9895 (19)	Ca4—O13	2.4319 (17)
Nb3—O9	1.843 (2)	Ca4—O11	2.497 (2)
Nb3—O8^i	1.8963 (18)	Ca4—O9	2.532 (2)
Nb3—O6^ii	1.984 (3)	Ca4—O8	2.552 (2)
Nb3—O7	1.997 (2)	Ca4—O10	2.559 (2)
Nb3—O3	2.100 (2)	Ca4—O7	3.1835 (17)
Nb3—O2^i	2.151 (2)	Ca4—O1	3.2138 (18)
Nb4—O10	1.850 (2)	Ca4—O5	3.332 (2)
Nb4—O11^i	1.8863 (18)	Ca4—O2	3.348 (2)
Nb4—O6	1.978 (3)	Ca5—O11	2.320 (2)
Nb4—O7	2.013 (2)	Ca5—O8^iv	2.343 (2)
Nb4—O4	2.114 (2)	Ca5—O6	2.3661 (19)
Nb4—O5^i	2.164 (2)	Ca5—O1^vi	2.5527 (18)
Nb5—O15	1.8401 (19)	Ca5—O4	2.752 (2)
Nb5—O14	1.841 (2)	Ca5—O2^iv	2.756 (2)
Nb5—O12^ii	1.998 (2)	Ca5—O3^iv	2.756 (2)
Nb5—O13	2.000 (2)	Ca5—O5	2.764 (2)
Nb5—O8	2.1197 (19)	Ca5—O12	2.8192 (18)
Nb5—O9	2.227 (2)	Ca5—O6^x	3.1205 (19)
Nb6—O17	1.798 (2)	Ca5—O9^iv	3.265 (2)
Nb6—O16	1.8660 (19)	Ca5—O10	3.304 (2)
Nb6—O12	1.980 (2)	O1—Ca3^x	2.366 (2)
Nb6—O13	2.022 (2)	O1—Ca5^vi	2.5527 (18)
Nb6—O11	2.1540 (19)	O2—Nb3^x	2.151 (2)
Nb6—O10	2.259 (2)	O2—Ca3^vii	2.383 (2)
Ca1—O17^i	2.303 (2)	O2—Ca3^x	2.678 (2)
Ca1—O14^iii	2.365 (2)	O2—Ca5^ii	2.756 (2)
Ca1—O15^iv	2.445 (2)	O3—Ca5^ii	2.756 (2)
Ca1—O15^v	2.454 (2)	O3—Ca3^ix	3.318 (2)
Ca1—O14^v	2.455 (2)	O4—Ca3^viii	3.304 (2)
Ca1—O16	2.472 (2)	O5—Nb4^x	2.164 (2)
Ca1—O12	2.5287 (18)	O5—Ca3^vi	2.367 (2)
Ca2—O17^i	2.398 (2)	O5—Ca3^x	2.659 (2)
Ca2—O15	2.398 (2)	O6—Nb3^iv	1.984 (2)
Ca2—O16^v	2.414 (2)	O6—Ca3^viii	2.9577 (19)
Ca2—O16	2.446 (2)	O6—Ca5^i	3.1205 (19)
Ca2—O14^i	2.506 (2)	O7—Ca4^i	2.3904 (17)
Ca2—O13^i	2.6428 (18)	O8—Nb3^x	1.8963 (18)
Ca2—O10	2.989 (2)	O8—Ca5^ii	2.343 (2)
Ca2—O9	3.094 (2)	O9—Ca5^ii	3.265 (2)
Ca2—O17^v	3.277 (2)	O11—Nb4^x	1.8863 (18)
Ca2—O13	3.4363 (19)	O12—Nb5^iv	1.998 (2)
Ca3—O1^i	2.366 (2)	O13—Ca2^x	2.6428 (18)
Ca3—O5^vi	2.367 (2)	O14—Ca1^xi	2.365 (2)
Ca3—O2^vii	2.383 (2)	O14—Ca1^xii	2.455 (2)
Ca3—O7	2.4050 (17)	O14—Ca2^x	2.506 (2)
Ca3—O4	2.644 (2)	O15—Ca1^ii	2.445 (2)
Ca3—O3	2.644 (2)	O15—Ca1^xii	2.454 (2)
Ca3—O5^i	2.659 (2)	O16—Ca2^xii	2.414 (2)
Ca3—O2^i	2.678 (2)	O17—Ca1^x	2.303 (2)
Ca3—O6^viii	2.9577 (19)	O17—Ca2^x	2.398 (2)
Ca3—O1	3.157 (2)	O17—Ca2^xii	3.277 (2)
O2^vii—Nb1—O2	180.00 (10)	O7^x—Ca4—O5	53.81 (6)
O2—Nb1—O1	89.97 (8)	O4—Ca4—O5	56.63 (7)
O2—Nb1—O1^vii	90.03 (8)	O3—Ca4—O5	108.29 (6)
O1—Nb1—O1^vii	180	O13—Ca4—O5	117.61 (7)
O2—Nb1—O3	91.97 (9)	O11—Ca4—O5	53.48 (6)
O1—Nb1—O3	91.12 (8)	O9—Ca4—O5	170.84 (6)
O2—Nb1—O3^vii	88.03 (9)	O8—Ca4—O5	121.17 (6)
O1—Nb1—O3^vii	88.88 (8)	O10—Ca4—O5	102.03 (6)
O3—Nb1—O3^vii	180.00 (7)	O7—Ca4—O5	113.25 (5)
O5—Nb2—O5^vi	180.00 (10)	O1—Ca4—O5	50.51 (5)
O5—Nb2—O1^vi	90.01 (8)	O7^x—Ca4—O2	53.40 (6)
O5—Nb2—O1	89.99 (8)	O4—Ca4—O2	108.50 (6)
O1^vi—Nb2—O1	180	O3—Ca4—O2	56.26 (7)
O5—Nb2—O4	91.85 (9)	O13—Ca4—O2	117.27 (6)
O1—Nb2—O4	91.31 (8)	O11—Ca4—O2	121.40 (6)
O5—Nb2—O4^vi	88.15 (9)	O9—Ca4—O2	100.49 (7)
O1—Nb2—O4^vi	88.69 (8)	O8—Ca4—O2	53.69 (6)
O4—Nb2—O4^vi	180.00 (7)	O10—Ca4—O2	170.46 (6)
O9—Nb3—O8^i	101.65 (9)	O7—Ca4—O2	112.69 (5)
O9—Nb3—O6^ii	98.52 (8)	O1—Ca4—O2	50.21 (5)
O8^i—Nb3—O6^ii	95.67 (8)	O5—Ca4—O2	82.49 (5)
O9—Nb3—O7	94.05 (8)	O11—Ca5—O8^iv	95.38 (6)
O8^i—Nb3—O7	90.67 (8)	O11—Ca5—O6	115.81 (8)
O6^ii—Nb3—O7	164.46 (7)	O8^iv—Ca5—O6	116.48 (8)
O9—Nb3—O3	87.97 (9)	O11—Ca5—O1^vi	124.01 (8)
O8^i—Nb3—O3	169.39 (9)	O8^iv—Ca5—O1^vi	124.90 (8)
O6^ii—Nb3—O3	87.22 (8)	O6—Ca5—O1^vi	81.93 (7)
O7—Nb3—O3	84.12 (7)	O11—Ca5—O4	76.37 (8)
O9—Nb3—O2^i	171.67 (9)	O8^iv—Ca5—O4	171.35 (7)
O8^i—Nb3—O2^i	85.65 (9)	O6—Ca5—O4	66.05 (8)
O6^ii—Nb3—O2^i	84.61 (7)	O1^vi—Ca5—O4	63.07 (6)
O7—Nb3—O2^i	81.75 (7)	O11—Ca5—O2^iv	117.25 (7)
O3—Nb3—O2^i	84.46 (9)	O8^iv—Ca5—O2^iv	64.88 (7)
O10—Nb4—O11^i	102.44 (9)	O6—Ca5—O2^iv	126.47 (8)
O10—Nb4—O6	99.03 (8)	O1^vi—Ca5—O2^iv	63.23 (6)
O11^i—Nb4—O6	96.59 (8)	O4—Ca5—O2^iv	121.06 (6)
O10—Nb4—O7	94.15 (8)	O11—Ca5—O3^iv	172.63 (8)
O11^i—Nb4—O7	90.26 (8)	O8^iv—Ca5—O3^iv	77.63 (7)
O6—Nb4—O7	163.44 (7)	O6—Ca5—O3^iv	66.25 (8)
O10—Nb4—O4	89.05 (9)	O1^vi—Ca5—O3^iv	62.84 (7)
O11^i—Nb4—O4	167.38 (9)	O4—Ca5—O3^iv	110.49 (5)
O6—Nb4—O4	86.60 (8)	O2^iv—Ca5—O3^iv	62.06 (6)
O7—Nb4—O4	83.63 (7)	O11—Ca5—O5	64.18 (7)
O10—Nb4—O5^i	171.90 (8)	O8^iv—Ca5—O5	116.98 (7)
O11^i—Nb4—O5^i	84.33 (9)	O6—Ca5—O5	126.22 (8)
O6—Nb4—O5^i	84.44 (7)	O1^vi—Ca5—O5	63.29 (7)
O7—Nb4—O5^i	81.25 (7)	O4—Ca5—O5	62.01 (7)
O4—Nb4—O5^i	83.83 (9)	O2^iv—Ca5—O5	73.59 (5)
O15—Nb5—O14	96.16 (9)	O3^iv—Ca5—O5	120.97 (6)
O15—Nb5—O12^ii	91.96 (8)	O11—Ca5—O12	65.84 (7)
O14—Nb5—O12^ii	100.21 (8)	O8^iv—Ca5—O12	65.03 (7)
O15—Nb5—O13	96.21 (8)	O6—Ca5—O12	79.03 (6)
O14—Nb5—O13	91.95 (8)	O1^vi—Ca5—O12	160.96 (7)
O12^ii—Nb5—O13	164.54 (7)	O4—Ca5—O12	108.50 (7)
O15—Nb5—O8	166.34 (8)	O2^iv—Ca5—O12	129.86 (7)
O14—Nb5—O8	97.50 (9)	O3^iv—Ca5—O12	108.54 (7)
O12^ii—Nb5—O8	85.78 (7)	O5—Ca5—O12	129.93 (7)
O13—Nb5—O8	83.19 (7)	O11—Ca5—O6^x	62.02 (7)
O15—Nb5—O9	86.33 (9)	O8^iv—Ca5—O6^x	61.61 (6)
O14—Nb5—O9	174.67 (8)	O6—Ca5—O6^x	176.32 (9)
O12^ii—Nb5—O9	84.38 (7)	O1^vi—Ca5—O6^x	101.75 (6)
O13—Nb5—O9	83.08 (7)	O4—Ca5—O6^x	115.34 (7)
O8—Nb5—O9	80.04 (8)	O2^iv—Ca5—O6^x	56.18 (6)
O17—Nb6—O16	100.66 (9)	O3^iv—Ca5—O6^x	115.50 (7)
O17—Nb6—O12	100.77 (8)	O5—Ca5—O6^x	56.14 (6)
O16—Nb6—O12	92.76 (9)	O12—Ca5—O6^x	97.29 (5)
O17—Nb6—O13	91.75 (8)	O11—Ca5—O9^iv	120.74 (7)
O16—Nb6—O13	96.73 (9)	O8^iv—Ca5—O9^iv	57.00 (7)
O12—Nb6—O13	162.63 (7)	O6—Ca5—O9^iv	59.48 (7)
O17—Nb6—O11	90.94 (9)	O1^vi—Ca5—O9^iv	113.98 (7)
O16—Nb6—O11	168.35 (8)	O4—Ca5—O9^iv	124.98 (6)
O12—Nb6—O11	86.07 (7)	O2^iv—Ca5—O9^iv	97.82 (6)
O13—Nb6—O11	81.70 (7)	O3^iv—Ca5—O9^iv	53.43 (6)
O17—Nb6—O10	168.62 (8)	O5—Ca5—O9^iv	171.38 (7)
O16—Nb6—O10	89.35 (9)	O12—Ca5—O9^iv	55.11 (6)
O12—Nb6—O10	83.98 (7)	O6^x—Ca5—O9^iv	118.57 (6)
O13—Nb6—O10	81.63 (7)	O11—Ca5—O10	56.73 (6)
O11—Nb6—O10	79.01 (8)	O8^iv—Ca5—O10	119.42 (6)
O17^i—Ca1—O14^iii	93.24 (6)	O6—Ca5—O10	59.09 (7)
O17^i—Ca1—O15^iv	159.76 (7)	O1^vi—Ca5—O10	114.48 (7)
O14^iii—Ca1—O15^iv	72.27 (8)	O4—Ca5—O10	53.85 (6)
O17^i—Ca1—O15^v	73.93 (7)	O2^iv—Ca5—O10	171.86 (6)
O14^iii—Ca1—O15^v	75.80 (7)	O3^iv—Ca5—O10	124.70 (6)
O15^iv—Ca1—O15^v	114.40 (4)	O5—Ca5—O10	98.34 (6)
O17^i—Ca1—O14^v	125.26 (8)	O12—Ca5—O10	54.65 (6)
O14^iii—Ca1—O14^v	112.79 (5)	O6^x—Ca5—O10	118.61 (6)
O15^iv—Ca1—O14^v	74.35 (7)	O9^iv—Ca5—O10	90.23 (5)
O15^v—Ca1—O14^v	67.82 (7)	Nb1—O1—Nb2	153.19 (11)
O17^i—Ca1—O16	73.94 (8)	Nb1—O1—Ca3^x	102.38 (8)
O14^iii—Ca1—O16	166.62 (8)	Nb2—O1—Ca3^x	101.55 (9)
O15^iv—Ca1—O16	119.07 (6)	Nb1—O1—Ca5^vi	92.00 (7)
O15^v—Ca1—O16	103.52 (7)	Nb2—O1—Ca5^vi	91.93 (7)
O14^v—Ca1—O16	78.57 (7)	Ca3^x—O1—Ca5^vi	108.12 (7)
O17^i—Ca1—O12	108.00 (7)	Nb1—O1—Ca3	77.18 (6)
O14^iii—Ca1—O12	114.18 (7)	Nb2—O1—Ca3	76.68 (6)
O15^iv—Ca1—O12	67.45 (7)	Ca3^x—O1—Ca3	166.08 (7)
O15^v—Ca1—O12	169.36 (6)	Ca5^vi—O1—Ca3	85.79 (5)
O14^v—Ca1—O12	103.67 (6)	Nb1—O1—Ca4	84.31 (6)
O16—Ca1—O12	67.69 (7)	Nb2—O1—Ca4	83.64 (6)
O17^i—Ca2—O15	164.60 (8)	Ca3^x—O1—Ca4	90.28 (5)
O17^i—Ca2—O16^v	80.00 (8)	Ca5^vi—O1—Ca4	161.60 (8)
O15—Ca2—O16^v	101.17 (7)	Ca3—O1—Ca4	75.81 (4)
O17^i—Ca2—O16	72.80 (7)	Nb1—O2—Nb3^x	152.80 (11)
O15—Ca2—O16	91.83 (6)	Nb1—O2—Ca3^vii	99.57 (8)
O16^v—Ca2—O16	95.58 (5)	Nb3^x—O2—Ca3^vii	107.29 (8)
O17^i—Ca2—O14^i	124.27 (6)	Nb1—O2—Ca3^x	92.56 (7)
O15—Ca2—O14^i	70.65 (7)	Nb3^x—O2—Ca3^x	86.88 (7)
O16^v—Ca2—O14^i	78.70 (7)	Ca3^vii—O2—Ca3^x	100.37 (8)
O16—Ca2—O14^i	159.80 (7)	Nb1—O2—Ca5^ii	86.37 (7)
O17^i—Ca2—O13^i	65.82 (7)	Nb3^x—O2—Ca5^ii	85.35 (7)
O15—Ca2—O13^i	129.03 (7)	Ca3^vii—O2—Ca5^ii	98.88 (7)
O16^v—Ca2—O13^i	93.52 (6)	Ca3^x—O2—Ca5^ii	160.62 (8)
O16—Ca2—O13^i	135.21 (7)	Nb1—O2—Ca4	80.81 (6)
O14^i—Ca2—O13^i	64.88 (7)	Nb3^x—O2—Ca4	72.15 (6)
O17^i—Ca2—O10	70.83 (7)	Ca3^vii—O2—Ca4	177.20 (9)
O15—Ca2—O10	103.60 (6)	Ca3^x—O2—Ca4	82.37 (5)
O16^v—Ca2—O10	148.05 (7)	Ca5^ii—O2—Ca4	78.36 (6)
O16—Ca2—O10	63.92 (6)	Nb1—O3—Nb3	156.05 (11)
O14^i—Ca2—O10	128.73 (7)	Nb1—O3—Ca4	109.03 (9)
O13^i—Ca2—O10	86.36 (6)	Nb3—O3—Ca4	94.51 (8)
O17^i—Ca2—O9	124.38 (7)	Nb1—O3—Ca3	90.94 (8)
O15—Ca2—O9	59.62 (6)	Nb3—O3—Ca3	88.80 (7)
O16^v—Ca2—O9	151.61 (7)	Ca4—O3—Ca3	100.95 (7)
O16—Ca2—O9	105.10 (6)	Nb1—O3—Ca5^ii	85.99 (7)
O14^i—Ca2—O9	75.20 (6)	Nb3—O3—Ca5^ii	86.90 (7)
O13^i—Ca2—O9	85.43 (6)	Ca4—O3—Ca5^ii	96.82 (7)
O10—Ca2—O9	60.29 (5)	Ca3—O3—Ca5^ii	161.98 (9)
O17^i—Ca2—O17^v	112.05 (5)	Nb1—O3—Ca3^ix	74.86 (6)
O15—Ca2—O17^v	58.15 (6)	Nb3—O3—Ca3^ix	81.47 (6)
O16^v—Ca2—O17^v	57.03 (6)	Ca4—O3—Ca3^ix	175.68 (8)
O16—Ca2—O17^v	63.48 (6)	Ca3—O3—Ca3^ix	80.65 (6)
O14^i—Ca2—O17^v	97.81 (6)	Ca5^ii—O3—Ca3^ix	81.41 (5)
O13^i—Ca2—O17^v	149.28 (5)	Nb2—O4—Nb4	156.22 (11)
O10—Ca2—O17^v	122.91 (5)	Nb2—O4—Ca4	108.92 (9)
O9—Ca2—O17^v	115.81 (6)	Nb4—O4—Ca4	94.49 (7)
O17^i—Ca2—O13	113.90 (6)	Nb2—O4—Ca3	90.44 (8)
O15—Ca2—O13	55.32 (6)	Nb4—O4—Ca3	88.86 (8)
O16^v—Ca2—O13	138.09 (6)	Ca4—O4—Ca3	101.49 (7)
O16—Ca2—O13	56.26 (6)	Nb2—O4—Ca5	86.21 (7)
O14^i—Ca2—O13	116.32 (6)	Nb4—O4—Ca5	87.00 (7)
O13^i—Ca2—O13	128.39 (6)	Ca4—O4—Ca5	96.73 (8)
O10—Ca2—O13	51.17 (5)	Ca3—O4—Ca5	161.57 (9)
O9—Ca2—O13	50.60 (5)	Nb2—O4—Ca3^viii	74.82 (6)
O17^v—Ca2—O13	81.54 (5)	Nb4—O4—Ca3^viii	81.67 (6)
O1^i—Ca3—O5^vi	113.14 (7)	Ca4—O4—Ca3^viii	175.92 (8)
O1^i—Ca3—O2^vii	112.42 (7)	Ca3—O4—Ca3^viii	79.91 (6)
O5^vi—Ca3—O2^vii	88.21 (6)	Ca5—O4—Ca3^viii	81.73 (5)
O1^i—Ca3—O7	86.80 (6)	Nb2—O5—Nb4^x	152.44 (11)
O5^vi—Ca3—O7	129.07 (8)	Nb2—O5—Ca3^vi	99.67 (8)
O2^vii—Ca3—O7	128.35 (7)	Nb4^x—O5—Ca3^vi	107.47 (8)
O1^i—Ca3—O4	131.74 (7)	Nb2—O5—Ca3^x	92.72 (8)
O5^vi—Ca3—O4	66.34 (7)	Nb4^x—O5—Ca3^x	87.40 (7)
O2^vii—Ca3—O4	115.75 (7)	Ca3^vi—O5—Ca3^x	99.91 (8)
O7—Ca3—O4	65.88 (6)	Nb2—O5—Ca5	86.34 (7)
O1^i—Ca3—O3	131.02 (7)	Nb4^x—O5—Ca5	84.75 (7)
O5^vi—Ca3—O3	115.67 (7)	Ca3^vi—O5—Ca5	99.06 (7)
O2^vii—Ca3—O3	65.96 (7)	Ca3^x—O5—Ca5	160.89 (8)
O7—Ca3—O3	65.70 (6)	Nb2—O5—Ca4	80.77 (6)
O4—Ca3—O3	74.06 (5)	Nb4^x—O5—Ca4	71.89 (5)
O1^i—Ca3—O5^i	67.27 (7)	Ca3^vi—O5—Ca4	177.05 (9)
O5^vi—Ca3—O5^i	80.09 (8)	Ca3^x—O5—Ca4	82.96 (5)
O2^vii—Ca3—O5^i	166.67 (7)	Ca5—O5—Ca4	78.04 (6)
O7—Ca3—O5^i	64.79 (7)	Nb4—O6—Nb3^iv	154.94 (10)
O4—Ca3—O5^i	65.22 (7)	Nb4—O6—Ca5	101.86 (10)
O3—Ca3—O5^i	125.06 (6)	Nb3^iv—O6—Ca5	101.37 (10)
O1^i—Ca3—O2^i	66.73 (7)	Nb4—O6—Ca3^viii	93.43 (7)
O5^vi—Ca3—O2^i	166.31 (8)	Nb3^iv—O6—Ca3^viii	93.27 (7)
O2^vii—Ca3—O2^i	79.63 (8)	Ca5—O6—Ca3^viii	96.26 (6)
O7—Ca3—O2^i	64.36 (7)	Nb4—O6—Ca5^i	78.68 (6)
O4—Ca3—O2^i	124.78 (6)	Nb3^iv—O6—Ca5^i	78.75 (6)
O3—Ca3—O2^i	64.94 (7)	Ca5—O6—Ca5^i	176.32 (9)
O5^i—Ca3—O2^i	111.19 (5)	Ca3^viii—O6—Ca5^i	80.07 (5)
O1^i—Ca3—O6^viii	73.70 (6)	Nb3—O7—Nb4	146.79 (9)
O5^vi—Ca3—O6^viii	61.94 (7)	Nb3—O7—Ca4^i	100.36 (8)
O2^vii—Ca3—O6^viii	61.76 (7)	Nb4—O7—Ca4^i	99.19 (8)
O7—Ca3—O6^viii	160.50 (6)	Nb3—O7—Ca3	98.36 (8)
O4—Ca3—O6^viii	128.24 (7)	Nb4—O7—Ca3	98.32 (8)
O3—Ca3—O6^viii	127.69 (6)	Ca4^i—O7—Ca3	113.06 (7)
O5^i—Ca3—O6^viii	106.57 (6)	Nb3—O7—Ca4	76.27 (5)
O2^i—Ca3—O6^viii	106.20 (7)	Nb4—O7—Ca4	75.91 (5)
O1^i—Ca3—O1	166.08 (7)	Ca4^i—O7—Ca4	159.15 (7)
O5^vi—Ca3—O1	58.73 (6)	Ca3—O7—Ca4	87.77 (5)
O2^vii—Ca3—O1	58.45 (6)	Nb3^x—O8—Nb5	145.31 (11)
O7—Ca3—O1	107.10 (5)	Nb3^x—O8—Ca5^ii	104.13 (8)
O4—Ca3—O1	57.91 (6)	Nb5—O8—Ca5^ii	106.76 (8)
O3—Ca3—O1	57.53 (6)	Nb3^x—O8—Ca4	97.81 (8)
O5^i—Ca3—O1	118.87 (6)	Nb5—O8—Ca4	89.21 (7)
O2^i—Ca3—O1	118.15 (6)	Ca5^ii—O8—Ca4	104.91 (8)
O6^viii—Ca3—O1	92.40 (5)	Nb3—O9—Nb5	154.71 (11)
O1^i—Ca3—O4^viii	55.80 (6)	Nb3—O9—Ca4	98.02 (9)
O5^vi—Ca3—O4^viii	57.73 (7)	Nb5—O9—Ca4	87.39 (7)
O2^vii—Ca3—O4^viii	114.41 (6)	Nb3—O9—Ca2	118.12 (9)
O7—Ca3—O4^viii	115.83 (6)	Nb5—O9—Ca2	83.11 (7)
O4—Ca3—O4^viii	100.09 (6)	Ca4—O9—Ca2	107.41 (7)
O3—Ca3—O4^viii	172.99 (7)	Nb3—O9—Ca5^ii	77.16 (7)
O5^i—Ca3—O4^viii	53.63 (6)	Nb5—O9—Ca5^ii	79.02 (6)
O2^i—Ca3—O4^viii	122.05 (6)	Ca4—O9—Ca5^ii	83.08 (6)
O6^viii—Ca3—O4^viii	52.94 (6)	Ca2—O9—Ca5^ii	158.85 (7)
O1—Ca3—O4^viii	116.22 (5)	Nb4—O10—Nb6	152.99 (11)
O1^i—Ca3—O3^ix	55.40 (6)	Nb4—O10—Ca4	96.64 (9)
O5^vi—Ca3—O3^ix	114.61 (6)	Nb6—O10—Ca4	87.08 (7)
O2^vii—Ca3—O3^ix	57.39 (7)	Nb4—O10—Ca2	119.22 (9)
O7—Ca3—O3^ix	115.11 (6)	Nb6—O10—Ca2	83.94 (6)
O4—Ca3—O3^ix	172.48 (6)	Ca4—O10—Ca2	109.82 (7)
O3—Ca3—O3^ix	99.35 (6)	Nb4—O10—Ca5	76.26 (7)
O5^i—Ca3—O3^ix	122.21 (6)	Nb6—O10—Ca5	77.90 (6)
O2^i—Ca3—O3^ix	53.21 (6)	Ca4—O10—Ca5	81.36 (6)
O6^viii—Ca3—O3^ix	52.99 (6)	Ca2—O10—Ca5	158.23 (8)
O1—Ca3—O3^ix	115.64 (5)	Nb4^x—O11—Nb6	142.09 (11)
O4^viii—Ca3—O3^ix	86.22 (4)	Nb4^x—O11—Ca5	105.15 (9)
O7^x—Ca4—O4	109.47 (7)	Nb6—O11—Ca5	106.68 (8)
O7^x—Ca4—O3	108.76 (7)	Nb4^x—O11—Ca4	99.19 (8)
O4—Ca4—O3	82.38 (6)	Nb6—O11—Ca4	90.99 (7)
O7^x—Ca4—O13	89.90 (6)	Ca5—O11—Ca4	106.57 (8)
O4—Ca4—O13	132.84 (8)	Nb6—O12—Nb5^iv	145.52 (9)
O3—Ca4—O13	132.55 (8)	Nb6—O12—Ca1	96.69 (8)
O7^x—Ca4—O11	68.85 (7)	Nb5^iv—O12—Ca1	96.43 (8)
O4—Ca4—O11	80.00 (7)	Nb6—O12—Ca5	95.24 (7)
O3—Ca4—O11	159.98 (7)	Nb5^iv—O12—Ca5	94.63 (7)
O13—Ca4—O11	67.33 (7)	Ca1—O12—Ca5	140.45 (7)
O7^x—Ca4—O9	134.67 (8)	Nb5—O13—Nb6	152.99 (10)
O4—Ca4—O9	114.30 (7)	Nb5—O13—Ca4	95.55 (8)
O3—Ca4—O9	67.18 (7)	Nb6—O13—Ca4	96.20 (8)
O13—Ca4—O9	68.88 (7)	Nb5—O13—Ca2^x	96.70 (7)
O11—Ca4—O9	129.40 (7)	Nb6—O13—Ca2^x	93.61 (7)
O7^x—Ca4—O8	68.10 (7)	Ca4—O13—Ca2^x	131.40 (7)
O4—Ca4—O8	160.45 (7)	Nb5—O13—Ca2	77.69 (6)
O3—Ca4—O8	80.33 (7)	Nb6—O13—Ca2	76.34 (6)
O13—Ca4—O8	66.56 (7)	Ca4—O13—Ca2	100.16 (6)
O11—Ca4—O8	115.15 (5)	Ca2^x—O13—Ca2	128.39 (6)
O9—Ca4—O8	66.75 (7)	Nb5—O14—Ca1^xi	134.87 (11)
O7^x—Ca4—O10	135.93 (8)	Nb5—O14—Ca1^xii	97.96 (8)
O4—Ca4—O10	68.15 (7)	Ca1^xi—O14—Ca1^xii	104.03 (7)
O3—Ca4—O10	114.20 (7)	Nb5—O14—Ca2^x	106.05 (9)
O13—Ca4—O10	68.30 (7)	Ca1^xi—O14—Ca2^x	108.08 (8)
O11—Ca4—O10	67.47 (7)	Ca1^xii—O14—Ca2^x	100.24 (8)
O9—Ca4—O10	73.79 (6)	Nb5—O15—Ca2	115.08 (9)
O8—Ca4—O10	127.88 (6)	Nb5—O15—Ca1^ii	103.86 (8)
O7^x—Ca4—O7	159.15 (7)	Ca2—O15—Ca1^ii	109.00 (8)
O4—Ca4—O7	56.97 (6)	Nb5—O15—Ca1^xii	98.04 (8)
O3—Ca4—O7	56.70 (6)	Ca2—O15—Ca1^xii	126.41 (8)
O13—Ca4—O7	110.94 (5)	Ca1^ii—O15—Ca1^xii	101.71 (7)
O11—Ca4—O7	118.98 (7)	Nb6—O16—Ca2^xii	115.88 (9)
O9—Ca4—O7	57.59 (6)	Nb6—O16—Ca2	110.19 (10)
O8—Ca4—O7	118.65 (7)	Ca2^xii—O16—Ca2	120.37 (8)
O10—Ca4—O7	57.84 (6)	Nb6—O16—Ca1	101.82 (9)
O7^x—Ca4—O1	69.85 (5)	Ca2^xii—O16—Ca1	102.37 (8)
O4—Ca4—O1	58.71 (6)	Ca2—O16—Ca1	103.05 (8)
O3—Ca4—O1	58.19 (6)	Nb6—O17—Ca1^x	139.98 (10)
O13—Ca4—O1	159.74 (6)	Nb6—O17—Ca2^x	108.68 (9)
O11—Ca4—O1	103.97 (6)	Ca1^x—O17—Ca2^x	109.96 (8)
O9—Ca4—O1	125.34 (7)	Nb6—O17—Ca2^xii	86.43 (7)
O8—Ca4—O1	103.88 (6)	Ca1^x—O17—Ca2^xii	100.36 (7)
O10—Ca4—O1	126.79 (6)	Ca2^x—O17—Ca2^xii	94.69 (6)
O7—Ca4—O1	89.31 (5)

Symmetry codes: (i) x, y, z−1; (ii) x−1, y, z; (iii) x+1, y, z−1; (iv) x+1, y, z; (v) −x+1, −y+3/2, z−1/2; (vi) −x+1, −y+1, −z+1; (vii) −x, −y+1, −z+1; (viii) −x+1, −y+1, −z; (ix) −x, −y+1, −z; (x) x, y, z+1; (xi) x−1, y, z+1; (xii) −x+1, −y+3/2, z+1/2.