A reinvestigation of the structure of Cs₃Ta₅O₁₄

In a recent analysis of a new pyrochlore-like mesoporous phase Rb₃Ta₅O₁₄ (trirubidium pentatantalum tetradecaoxide) [du Boulay et al. (2002). Acta Cryst. C58, i40–i44], the authors observed in the literature some rather large uncertainties in the vibrational motion and thereby atomic positions reported for the archetypal analogue structure Cs₃Ta₅O₁₄. New X-ray diffraction data for that compound were collected on an image plate diffractometer with an Mo Kα source. The current study confirms the original structural model and modestly improves on its precision.

Key indicators

• Single-crystal X-ray study
• T = 295 K
• Mean [sigma](Ta-O) = 0.007 Å
• R factor = 0.044
• wR factor = 0.032
• Data-to-parameter ratio = 19.4

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



PLAT_213  Alert C Atom O3      has ADP max/min Ratio ...........       3.20 oblate

PLAT_213  Alert C Atom O9      has ADP max/min Ratio ...........       3.50 oblate

General Notes



FORMU_01  There is a discrepancy between the atom counts in the
          _chemical_formula_sum and _chemical_formula_moiety. This is
          usually due to the moiety formula being in the wrong format.
          Atom count from _chemical_formula_sum:   Cs3 O14 Ta5
          Atom count from _chemical_formula_moiety:O14 Rb3 Ta5


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 2 Alert Level C = Please check

---

S1. Comment

In the course of investigation of four layered Rb₂Ca₂Ta₄O₁₃ perovskites a new mesoporous pyrochlore like structural phase, Rb₃Ta₅O₁₄, was encountered by du Boulay et al. (2002). That phase turned out to be a variant of a Cs₃Ta₅O₁₄ archetype structure reported previously by Serafin & Hoppe (1982). In reviewing the two structures, the more recent authors were led to suspect some irregularities in the original Cs₃Ta₅O₁₄ structural model because, with the exception of three independent Cs sites, all atoms were refined with isotropic displacement parameters and of the Cs sites, two exhibited unusually large U^ij values. The isotropic displacement parameters of the O atoms also varied considerably over the range 0.001–0.023 Ų. The largest displacement parameter occurred for one atom, Cs3, located on one of two independent Pbam mirror planes which exhibited very large displacements normal to that plane. Consequently du Boulay et al. (2002) speculated that the mirror symmetry could be broken, by analogy with two of the Rb atoms in the Rb₃Ta₅O₁₄ analogue. This could have led to doubling of the Pbam c axis and a Cs-atom sublattice in closer agreement with the Rb sublattice observed for the latter compound.

To remove any uncertainties the current authors crystalized and reanalysed Cs₃Ta₅O₁₄ via single-crystal X-ray diffraction. Here we confirm that the structure reported by Serafin & Hoppe (1982) was correct and, in addition, we report marginally more precise structural parameters accompanied by anisotropic displacement parameters determined for all atoms.

X-Ray fluorescence image plate data for Cs₃Ta₅O₁₄ were measured on a Rigaku R-AXIS RAPID three-circle diffractometer. An Mo Kα X-ray source and a semi-cylindrical fluorescence plate were used to measure the room temperature single-crystal diffraction data. The initial orientation matrix and associated lattice parameters were determined from eight oscillation photos measured at 120 s per ° with Δω = 2°. A single 90 min duration X-ray image was taken while rotating the crystal 30° about its c axis at 180 s per °. That frame failed to reveal superlattice reflections of any kind along the Pbam c axis. The implications being that the originally reported lattice was quite correct, though not necessarily the symmetry.

The data measurement involved 275 image plate frames measured with rotations of Δω = 2° at 500 s per ° from which 20976 reflections were identified out to 2θ ≤ 60.1°. Lattice parameters were refined with other apparatus parameters using all 275 frames and agree with those of Serafin & Hoppe (1982) to about 0.05 Å. The measured intensities were in good accord with the b-glide along a and a-glide along b reported by the previous authors. The uncertainties remaining therefore primarily concern the degree of perfection of the Pbam mirror planes.

Structurally Cs₃Ta₅O₁₄ consists of four distinct TaO polyhedra, of which three are corner-sharing TaO₆ octahedra and one is an edge-sharing TaO₅ bicapped trigonal prism, as depicted in Fig. 1. Those TaO polyhedra form the backbone of a network of two symmetry distinct, Cs filled structural cavities, the larger containing four Cs atoms with the smaller cavity containing two. The underlying atomic coordination geometries were well examined by Serafin & Hoppe (1982), and the relationship of Cs₃Ta₅O₁₄ to the three independent cavity network of mesoporous Rb₃Ta₅O₁₄ was previously discussed by du Boulay et al. (2002).

S2. Experimental

Reagent grade CsCl and Ta₂O₅ chemicals 4.245 g in total, were combined to form 0.1 mol% Cs₃Ta₅O₁₄ in a 99.9 mol% CsCl flux. In a Pt crucible, the mixture was heated quickly to 1073 K, which was sustained for 2 h and followed by slow cooling at 2.8 K h⁻¹ to 723 K. After rinsing in hot water, the residue contained transparent and colourless crystals of Cs₃Ta₅O₁₄ with rectangular shapes as well as unidentified crystals with thin hexagonal shapes.

S3. Refinement

Although minor difficulties were encountered refining the structure because of a tendency toward non-positive definite displacement parameters for two O atoms, the problems were supressed after including all data satisfying F² ≥ 0 in a refinement on F, in conjunction with a modified weighting scheme. This led to a larger but acceptible R factor wR(F) = 0.032. The refined atomic positions agree with those of Serafin & Hoppe (1982) typically within two of their reported s.u.'s, although the s.u.'s reported here are typically smaller by a factor of about 5. The mean atomic displacement parameters are also comparable in magnitude between the two studies, though herein U_eq for the Ta atoms are about double that reported in the earlier work. In addition, U_eq values for the O atoms reported here have a considerably smaller dynamic range. The anisotropic vibration tensor elements for the Cs atoms are broadly comparable between the experiments, though disparities of up to a factor of 2 on some components are to be found. U_eq values reported here for the Cs atoms are typically half the magnitude of equivalent parameters determined for the four Rb atoms in Rb₃Ta₅O₁₄ by du Boulay et al. (2002). In particular, the largest vibration tensor component observed herein (U₃₃ = 0.0472 Ų for Cs3) is less than half that of the largest tensor element reported in the latter [U₂₂ = 0.1057 (11) Ų for Rb4]. The large Cs atom vibrations are in good accord with the structural geometry because they occupy large structural cavities with asymmetric bonding environments. This is particularly true of Cs3 which has one short Cs3—O6 bond within the plane that appears to act like a hinge on which the Cs3 atom can swing with greater freedom into two adjoining structural cavities.

A relatively large residual Δρ range was observed [−4(1) to 4(1) e Å⁻³]. The two largest peaks occur 0.7 Å away from Cs1 and 0.8 Å from O4 and both maxima occur on the z=0 mirror plane. The two largest holes were also located on the mirror planes, 1.7 Å from Cs1 and 1.5 Å from Cs2. The positions and magnitudes of the extrema suggest a stochastic measurement noise origin, rather than a deficiency of the harmonic vibration model of the atoms. The experimental electron density does then seem to be in good accord with the Pbam space group symmetry.

As a further check, the data were refined against a lower symmetry Pba2 structural model yielding wR(F) = 0.029 from 199 parameters and 2269 reflections, with 14 of the 23 independent atoms exhibiting non-positive definite atomic displacement parameters and only minor changes in the atomic displacement parameters of the Cs atoms. Comparable results were obtained using P2₁2₁2 with wR(F) = 0.032 from 200 parameters and 12 atoms non-positive-definite. Although Pba2 symmetry superficially reduces the R factor, it introduces around 25% more atoms and 70% more parameters which do not really improve the structural model. Especially, there was no significant damping effects on the mean squared displacement parameters of the Cs atoms.

We conclude therefore that the adoption of a symmetry lower than Pbam gives no significant improvement over the structural model originally proposed by Seraffin & Hoppe (1982), though the current confirmatory study has modestly improved upon the accuracy of the original and full anisotropic displacement parameters are reported here for all atoms.

Computing details

Data collection: RAPID-AUTO (Rigaku, 1999); cell refinement: RAPID-AUTO; data reduction: RAPID-AUTO; program(s) used to solve structure: Serafin & Hoppe (1982); program(s) used to refine structure: CRYLSQ in Xtal3.7 (Hall et al., 2000); molecular graphics: ATOMS (Dowty, 1999) and ORTEP in Xtal3.7; software used to prepare material for publication: Xtal BONDLA CIFIO in Xtal3.7.

Figures

Fig. 1. ATOMS (Dowty, 1999) polyhedral view of the Pbam Cs3Ta5O14 lattice as projected along (a) the b axis and (b) the c axis. Ellipsoids are rendered at the 90° probability level. Fivefold polyhedra are coloured brown.

Fig. 2. ORTEP (Xtal3.7; Hall et al., 2001) view of an extended asymmetric subunit, with ellipsoids rendered at the 99° probability level. [Symmetry codes: (i) −x, −y, z; (ii) 1/2 + x, 1/2 − y, −z; (iii) 1/2 − x, 1/2 + y, −z; (iv) x, y, −z; (v) 1/2 − x, 1/2 + y, z; (vi) −1/2 + x, 1/2 − y, z; (vii) −x, 1 − y, z; (viii) 1/2 − x, −1/2 + y, −z; (ix) 1/2 − x, −1/2 + y, z; (x) x, y, 1 + z; (xi) x, y, 1 − z; (xii) 1/2 − x, −1/2 + y, 1 − z.]

(I)

Crystal data

Cs3Ta5O14	F(000) = 2568
Mr = 1527.48	Dx = 7.048 Mg m^−3
Orthorhombic, Pbam	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -p 2 2ab	Cell parameters from 20976 reflections
a = 26.219 (6) Å	θ = 1.6–30.0°
b = 7.4283 (10) Å	µ = 45.17 mm^−1
c = 7.3914 (10) Å	T = 295 K
V = 1439.6 (4) Å^3	Rectangular block, colourless
Z = 4	0.06 × 0.06 × 0.04 mm

Data collection

Rigaku Rapid image plate diffractometer	2269 independent reflections
Radiation source: Mo Kα tube	2269 reflections with F > 0
Graphite monochromator	Rint = 0.060
ω scans	θmax = 30.0°, θmin = 1.6°
Absorption correction: numerical Gaussian integration on 8× 8× 8 grid	h = 0→36
Tmin = 0.113, Tmax = 0.349	k = −10→0
2269 measured reflections	l = 0→10

Refinement

Refinement on F	0 restraints
Least-squares matrix: full	0 constraints
R[F^2 > 2σ(F^2)] = 0.044	w = 1/[σ(F)^2 + 0.2 + 10^-4F^2]
wR(F^2) = 0.032	(Δ/σ)max = 0.001
S = 0.91	Δρmax = 3.69 e Å^−3
2269 reflections	Δρmin = −4.25 e Å^−3
117 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cs1	0.29149 (4)	0.15909 (17)	0.00000	0.0270 (5)
Cs2	0.02229 (3)	0.24078 (16)	0.50000	0.0241 (5)
Cs3	0.38046 (3)	0.15651 (15)	0.50000	0.0279 (5)
Ta1	0.054631 (18)	0.42585 (7)	0.00000	0.0071 (2)
Ta2	0.442909 (18)	0.41007 (7)	0.00000	0.0062 (2)
Ta3	0.25378 (2)	0.40034 (7)	0.50000	0.0066 (2)
Ta4	0.151840 (12)	0.16072 (5)	0.25490 (4)	0.00671 (15)
O1	0.00000	0.50000	0.1740 (11)	0.012 (4)
O2	0.0162 (3)	0.1597 (14)	0.00000	0.012 (4)
O3	0.1671 (3)	0.1326 (14)	0.00000	0.012 (4)
O4	0.4189 (3)	0.1719 (15)	0.00000	0.017 (5)
O5	0.1250 (3)	0.1554 (14)	0.50000	0.012 (4)
O6	0.2718 (3)	0.1448 (14)	0.50000	0.012 (4)
O7	0.2009 (2)	0.3374 (9)	0.3059 (8)	0.009 (3)
O8	0.3039 (2)	0.4561 (9)	0.6882 (8)	0.009 (3)
O9	0.0979 (2)	0.3408 (9)	0.1915 (8)	0.010 (3)
O10	0.4110 (2)	0.4733 (9)	0.2075 (8)	0.013 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cs1	0.0265 (4)	0.0288 (6)	0.0256 (4)	−0.0013 (5)	0.00000	0.00000
Cs2	0.0168 (4)	0.0293 (6)	0.0262 (4)	0.0030 (4)	0.00000	0.00000
Cs3	0.0132 (4)	0.0233 (5)	0.0472 (6)	0.0018 (4)	0.00000	0.00000
Ta1	0.0067 (2)	0.0065 (3)	0.0080 (2)	0.0008 (2)	0.00000	0.00000
Ta2	0.0062 (2)	0.0061 (2)	0.0063 (2)	0.00050 (19)	0.00000	0.00000
Ta3	0.0079 (2)	0.0049 (2)	0.00709 (18)	−0.00035 (19)	0.00000	0.00000
Ta4	0.00809 (14)	0.00738 (18)	0.00465 (14)	−0.00007 (13)	−0.00051 (11)	−0.00051 (15)
O1	0.014 (4)	0.014 (5)	0.008 (3)	0.002 (4)	0.00000	0.00000
O2	0.009 (3)	0.009 (5)	0.017 (4)	−0.001 (4)	0.00000	0.00000
O3	0.017 (4)	0.016 (5)	0.002 (3)	0.004 (4)	0.00000	0.00000
O4	0.012 (4)	0.017 (5)	0.021 (4)	0.009 (4)	0.00000	0.00000
O5	0.008 (4)	0.013 (5)	0.015 (4)	0.001 (4)	0.00000	0.00000
O6	0.009 (4)	0.009 (5)	0.017 (4)	−0.006 (4)	0.00000	0.00000
O7	0.009 (2)	0.010 (3)	0.008 (2)	−0.001 (2)	−0.002 (2)	0.002 (3)
O8	0.010 (2)	0.007 (3)	0.009 (3)	−0.001 (2)	−0.003 (2)	−0.002 (3)
O9	0.008 (2)	0.014 (3)	0.009 (3)	0.002 (2)	−0.007 (2)	−0.002 (3)
O10	0.011 (2)	0.012 (3)	0.017 (3)	0.003 (3)	0.005 (2)	0.006 (3)

Geometric parameters (Å, º)

Cs1—O8	3.207 (6)	Cs3—O9	3.320 (6)
Cs1—O8	3.207 (6)	Cs3—O9	3.320 (6)
Cs1—O3	3.268 (9)	Ta1—O9^iii	1.920 (6)
Cs1—O7	3.296 (6)	Ta1—O9	1.920 (6)
Cs1—O7	3.296 (6)	Ta1—O4^i	1.955 (11)
Cs1—O4	3.342 (9)	Ta1—O1	2.002 (5)
Cs1—Cs1^i	4.3046 (17)	Ta1—O1	2.002 (5)
Cs1—Cs1	4.3046 (17)	Ta1—O2	2.219 (10)
Cs1—Cs3	4.3704 (9)	Ta2—O10^iii	1.808 (6)
Cs1—Cs3	4.3704 (9)	Ta2—O10	1.808 (6)
Cs2—O5	2.767 (8)	Ta2—O4	1.878 (11)
Cs2—O9	3.111 (6)	Ta2—O2^iv	1.991 (8)
Cs2—O9	3.111 (6)	Ta2—O2^i	2.141 (10)
Cs2—O1	3.140 (6)	Ta3—O6	1.936 (10)
Cs2—O1	3.140 (6)	Ta3—O6	1.956 (10)
Cs2—O10	3.417 (6)	Ta3—O8	1.959 (6)
Cs2—O10	3.417 (6)	Ta3—O8	1.959 (6)
Cs2—Cs2^ii	3.7634 (18)	Ta3—O7	2.050 (6)
Cs2—Cs3	3.7961 (15)	Ta3—O7	2.050 (6)
Cs2—Cs3	4.0047 (16)	Ta4—O7	1.876 (6)
Cs2—Cs2	4.0247 (18)	Ta4—O3	1.937 (2)
Cs3—O6	2.851 (8)	Ta4—O5	1.944 (3)
Cs3—O10	3.294 (7)	Ta4—O8	1.957 (6)
Cs3—O10	3.294 (7)	Ta4—O9	2.003 (6)
Cs3—O8	3.304 (6)	Ta4—O10	2.186 (6)
Cs3—O8	3.304 (6)
O8—Cs1—O8	91.87 (16)	O10—Cs3—Cs1	64.65 (11)
O8—Cs1—O3	98.22 (16)	O8—Cs3—O8	49.82 (14)
O8—Cs1—O7	89.98 (15)	O8—Cs3—O9	106.89 (15)
O8—Cs1—O7	170.26 (14)	O8—Cs3—O9	150.35 (14)
O8—Cs1—O4	83.03 (16)	O8—Cs3—Cs2	117.36 (11)
O8—Cs1—Cs1^i	57.17 (11)	O8—Cs3—Cs2	154.98 (10)
O8—Cs1—Cs1	130.17 (11)	O8—Cs3—Cs1	91.66 (10)
O8—Cs1—Cs3	123.80 (11)	O8—Cs3—Cs1	46.90 (10)
O8—Cs1—Cs3	48.78 (11)	O8—Cs3—O9	150.35 (14)
O8—Cs1—O3	98.22 (16)	O8—Cs3—O9	106.89 (14)
O8—Cs1—O7	170.26 (14)	O8—Cs3—Cs2	117.36 (11)
O8—Cs1—O7	89.98 (15)	O8—Cs3—Cs2	154.98 (10)
O8—Cs1—O4	83.03 (16)	O8—Cs3—Cs1	46.90 (10)
O8—Cs1—Cs1^i	57.17 (11)	O8—Cs3—Cs1	91.66 (10)
O8—Cs1—Cs1	130.17 (10)	O9—Cs3—O9	86.77 (16)
O8—Cs1—Cs3	48.78 (11)	O9—Cs3—Cs2	88.53 (10)
O8—Cs1—Cs3	123.80 (11)	O9—Cs3—Cs2	49.18 (10)
O3—Cs1—O7	90.97 (16)	O9—Cs3—Cs1	132.48 (11)
O3—Cs1—O7	90.97 (16)	O9—Cs3—Cs1	60.90 (10)
O3—Cs1—O4	178.2 (3)	O9—Cs3—Cs2	88.53 (10)
O3—Cs1—Cs1^i	63.09 (19)	O9—Cs3—Cs2	49.18 (10)
O3—Cs1—Cs1	56.18 (19)	O9—Cs3—Cs1	60.90 (10)
O3—Cs1—Cs3	122.177 (18)	O9—Cs3—Cs1	132.48 (11)
O3—Cs1—Cs3	122.177 (18)	Cs2—Cs3—Cs2	62.05 (3)
O7—Cs1—O7	86.64 (15)	Cs2—Cs3—Cs1	121.466 (18)
O7—Cs1—O4	87.70 (16)	Cs2—Cs3—Cs1	121.466 (18)
O7—Cs1—Cs1^i	131.01 (10)	Cs2—Cs3—Cs1	110.07 (2)
O7—Cs1—Cs1	53.50 (10)	Cs2—Cs3—Cs1	110.07 (2)
O7—Cs1—Cs3	123.00 (11)	Cs1—Cs3—Cs1	115.48 (3)
O7—Cs1—Cs3	51.99 (10)	O9^iii—Ta1—O9	95.0 (2)
O7—Cs1—O4	87.70 (16)	O9^iii—Ta1—O4^i	95.6 (3)
O7—Cs1—Cs1^i	131.01 (10)	O9^iii—Ta1—O1	92.3 (2)
O7—Cs1—Cs1	53.50 (10)	O9^iii—Ta1—O1	170.5 (2)
O7—Cs1—Cs3	51.99 (10)	O9^iii—Ta1—O2	88.5 (2)
O7—Cs1—Cs3	123.00 (11)	O9—Ta1—O4^i	95.6 (3)
O4—Cs1—Cs1^i	118.73 (19)	O9—Ta1—O1	170.5 (2)
O4—Cs1—Cs1	121.99 (19)	O9—Ta1—O1	92.3 (2)
O4—Cs1—Cs3	57.763 (17)	O9—Ta1—O2	88.5 (2)
O4—Cs1—Cs3	57.763 (17)	O4^i—Ta1—O1	89.8 (2)
Cs1^i—Cs1—Cs1	119.27 (3)	O4^i—Ta1—O1	89.8 (2)
Cs1^i—Cs1—Cs3	105.88 (2)	O4^i—Ta1—O2	173.8 (4)
Cs1^i—Cs1—Cs3	105.88 (2)	O1—Ta1—O1	79.9 (3)
Cs1—Cs1—Cs3	105.43 (3)	O1—Ta1—O2	85.45 (17)
Cs1—Cs1—Cs3	105.43 (3)	O1—Ta1—O2	85.45 (17)
Cs3—Cs1—Cs3	115.48 (3)	O10^iii—Ta2—O10	116.0 (3)
O5—Cs2—O9	55.59 (14)	O10^iii—Ta2—O4	95.1 (3)
O5—Cs2—O9	55.59 (14)	O10^iii—Ta2—O2^iv	120.9 (2)
O5—Cs2—O1	108.77 (13)	O10^iii—Ta2—O2^i	90.4 (2)
O5—Cs2—O1	108.77 (13)	O10—Ta2—O4	95.1 (3)
O5—Cs2—O10	50.87 (16)	O10—Ta2—O2^iv	120.9 (2)
O5—Cs2—O10	50.87 (16)	O10—Ta2—O2^i	90.4 (2)
O5—Cs2—Cs2^ii	94.8 (2)	O4—Ta2—O2^iv	94.5 (4)
O5—Cs2—Cs3	178.3 (2)	O4—Ta2—O2^i	169.6 (4)
O5—Cs2—Cs3	63.7 (2)	O2^iv—Ta2—O2^i	75.1 (4)
O5—Cs2—Cs2	120.1 (2)	O6—Ta3—O6	173.7 (4)
O9—Cs2—O9	94.29 (15)	O6—Ta3—O8	91.9 (3)
O9—Cs2—O1	53.80 (12)	O6—Ta3—O8	91.9 (3)
O9—Cs2—O1	122.33 (14)	O6—Ta3—O7	88.8 (3)
O9—Cs2—O10	106.08 (15)	O6—Ta3—O7	88.8 (3)
O9—Cs2—O10	49.41 (17)	O6—Ta3—O8	92.5 (3)
O9—Cs2—Cs2^ii	115.14 (13)	O6—Ta3—O8	92.5 (3)
O9—Cs2—Cs3	125.16 (11)	O6—Ta3—O7	86.7 (3)
O9—Cs2—Cs3	53.87 (12)	O6—Ta3—O7	86.7 (3)
O9—Cs2—Cs2	87.50 (12)	O8—Ta3—O8	90.5 (2)
O9—Cs2—O1	122.33 (14)	O8—Ta3—O7	178.8 (3)
O9—Cs2—O1	53.80 (12)	O8—Ta3—O7	90.3 (2)
O9—Cs2—O10	49.41 (17)	O8—Ta3—O7	90.3 (2)
O9—Cs2—O10	106.08 (15)	O8—Ta3—O7	178.8 (3)
O9—Cs2—Cs2^ii	115.14 (12)	O7—Ta3—O7	88.8 (2)
O9—Cs2—Cs3	125.16 (11)	O7—Ta4—O3	97.4 (3)
O9—Cs2—Cs3	53.87 (12)	O7—Ta4—O5	94.3 (3)
O9—Cs2—Cs2	87.50 (12)	O7—Ta4—O8	95.4 (3)
O1—Cs2—O1	100.27 (14)	O7—Ta4—O9	93.7 (3)
O1—Cs2—O10	159.63 (11)	O7—Ta4—O10	174.2 (2)
O1—Cs2—O10	88.07 (14)	O3—Ta4—O5	168.2 (4)
O1—Cs2—Cs2^ii	121.68 (7)	O3—Ta4—O8	90.2 (3)
O1—Cs2—Cs3	72.20 (4)	O3—Ta4—O9	89.4 (3)
O1—Cs2—Cs3	69.24 (5)	O3—Ta4—O10	86.0 (3)
O1—Cs2—Cs2	50.14 (10)	O5—Ta4—O8	89.9 (3)
O1—Cs2—O10	88.07 (14)	O5—Ta4—O9	88.6 (3)
O1—Cs2—O10	159.63 (11)	O5—Ta4—O10	82.2 (3)
O1—Cs2—Cs2^ii	121.68 (7)	O8—Ta4—O9	170.9 (2)
O1—Cs2—Cs3	72.20 (4)	O8—Ta4—O10	89.2 (2)
O1—Cs2—Cs3	69.24 (5)	O9—Ta4—O10	81.7 (2)
O1—Cs2—Cs2	50.14 (10)	Ta1—O1—Ta1	100.1 (4)
O10—Cs2—O10	78.49 (15)	Ta1—O1—Cs2	142.64 (9)
O10—Cs2—Cs2^ii	66.80 (11)	Ta1—O1—Cs2	101.01 (8)
O10—Cs2—Cs3	128.16 (10)	Ta1—O1—Cs2	101.01 (8)
O10—Cs2—Cs3	97.05 (11)	Ta1—O1—Cs2	142.64 (10)
O10—Cs2—Cs2	134.83 (11)	Cs2—O1—Cs2	79.7 (2)
O10—Cs2—Cs2^ii	66.80 (11)	Ta2—O2—Ta2	104.9 (4)
O10—Cs2—Cs3	128.16 (10)	Ta2—O2—Ta1	132.1 (5)
O10—Cs2—Cs3	97.05 (11)	Ta2—O2—Ta1	123.0 (4)
O10—Cs2—Cs2	134.83 (11)	Ta4^iii—O3—Ta4	153.1 (5)
Cs2^ii—Cs2—Cs3	83.50 (3)	Ta4^iii—O3—Cs1	101.5 (3)
Cs2^ii—Cs2—Cs3	158.56 (3)	Ta4—O3—Cs1	101.5 (3)
Cs2^ii—Cs2—Cs2	145.02 (3)	Ta2—O4—Ta1	139.6 (5)
Cs3—Cs2—Cs3	117.95 (4)	Ta2—O4—Cs1	111.2 (4)
Cs3—Cs2—Cs2	61.52 (3)	Ta1—O4—Cs1	109.1 (4)
Cs3—Cs2—Cs2	56.43 (3)	Ta4—O5—Ta4	137.5 (4)
O6—Cs3—O10	105.37 (18)	Ta4—O5—Cs2	110.3 (2)
O6—Cs3—O10	105.37 (18)	Ta4—O5—Cs2	110.3 (2)
O6—Cs3—O8	54.1 (2)	Ta3—O6—Ta3	145.8 (5)
O6—Cs3—O8	54.1 (2)	Ta3—O6—Cs3	112.0 (4)
O6—Cs3—O9	98.60 (17)	Ta3—O6—Cs3	102.2 (4)
O6—Cs3—O9	98.60 (17)	Ta4—O7—Ta3	139.8 (3)
O6—Cs3—Cs2	170.2 (2)	Ta4—O7—Cs1^i	114.3 (2)
O6—Cs3—Cs2	127.8 (2)	Ta3—O7—Cs1^i	105.9 (2)
O6—Cs3—Cs1	57.766 (17)	Ta4—O8—Ta3	135.6 (3)
O6—Cs3—Cs1	57.766 (17)	Ta4—O8—Cs1	116.1 (2)
O10—Cs3—O10	82.03 (16)	Ta4—O8—Cs3	104.7 (2)
O10—Cs3—O8	86.74 (15)	Ta3—O8—Cs1	107.3 (2)
O10—Cs3—O8	52.43 (14)	Ta3—O8—Cs3	88.1 (2)
O10—Cs3—O9	156.01 (14)	Cs1—O8—Cs3	84.32 (15)
O10—Cs3—O9	90.69 (16)	Ta1—O9—Ta4	144.0 (3)
O10—Cs3—Cs2	67.55 (10)	Ta1—O9—Cs2	104.1 (2)
O10—Cs3—Cs2	113.32 (11)	Ta1—O9—Cs3	112.0 (3)
O10—Cs3—Cs1	64.65 (11)	Ta4—O9—Cs2	96.8 (2)
O10—Cs3—Cs1	132.98 (12)	Ta4—O9—Cs3	101.0 (2)
O10—Cs3—O8	52.43 (14)	Cs2—O9—Cs3	76.95 (14)
O10—Cs3—O8	86.74 (15)	Ta2—O10—Ta4^v	130.5 (3)
O10—Cs3—O9	90.69 (16)	Ta2—O10—Cs3	118.9 (3)
O10—Cs3—O9	156.01 (14)	Ta2—O10—Cs2	116.8 (3)
O10—Cs3—Cs2	67.55 (10)	Ta4^v—O10—Cs3	99.6 (2)
O10—Cs3—Cs2	113.32 (11)	Ta4^v—O10—Cs2	85.1 (2)
O10—Cs3—Cs1	132.98 (12)	Cs3—O10—Cs2	97.16 (16)

Symmetry codes: (i) −x+1/2, y+1/2, −z; (ii) −x, −y, z; (iii) x, y, −z; (iv) x+1/2, −y+1/2, −z; (v) −x+1/2, y+1/2, z.