Ca2Te3O8, a new phase in the CaO-TeO2 system.

Single crystals of dicalcium octa-oxidotritellurate(IV), Ca2Te3O8, were obtained from a CsCl/NaCl melt with CaO and TeO2 as educts in the molar ratio of 1:2. Ca2Te3O8 crystallizes isotypically with Pb3Te2O8 and is comprised of two unique Ca, four Te and eight O sites. One calcium cation has eight and the other nine coordination partners. Both coordination polyhedra are considerably distorted. Two kinds of oxotellurate(IV) anions with the same formula [Te3O8]4- are present. One is an infinite zigzag chain anion consisting of pairs of [TeO4] bis-phenoids linked to a trigonal-pyramidal [TeO3] group with a connectivity of [(TeO1/1O2/2)(TeO2/1O2/2)2] n , while the other is a finite anion made up of one central [TeO4] bis-phenoid linked to two [TeO3] trigonal pyramids and has a connectivity of [(TeO2/1O1/2)2(TeO2/2O2/1)]. In the crystal, the anions are organized in layers extending parallel to (100). Adjacent layers are held together by the calcium cations to define a three-dimensional framework structure.

Chemical context

A partial phase diagram for the pseudo-binary system CaO–TeO2 has been determined for the composition range 50–100 mol% TeO2 to contain the 1:1 phase CaTeO3 and the 1:2 phase CaTe2O5 (Mishra et al., 1998 ▸). Another phase not reported during the original study of Mishra et al. (1998 ▸) is the 4:5 phase Ca4Te5O14, for which full structural details were determined for the normal-pressure and high-pressure forms (Weil, 2004 ▸; Weil et al., 2016 ▸). For compositions CaTeO3 and CaTe2O5, polymorphism was reported on the basis of differential thermal analysis and temperature-dependent X-ray diffracion (Mishra et al., 1998 ▸; Tripathi et al., 2001 ▸), however, without structural details of the corresponding phases. Whereas crystal structure determinations were subsequently performed for four polymorphic forms of CaTeO3 (Stöger et al., 2009 ▸; Poupon et al., 2015 ▸), our present knowledge of the CaTe2O5 structures is restricted to only one form (Weil & Stöger, 2008 ▸; Barrier et al., 2009 ▸) that is not related to the mica-like CaTe2O5 phase reported nearly 50 years ago (Redman et al., 1970 ▸). In an attempt to grow single crystals of the latter from a salt melt at comparatively low temperatures, a heretofore unknown phase in the CaO–TeO2 system was obtained, viz. the 2:3 phase Ca2Te3O8.

In this article, preparation conditions, crystal structure and the relation to the isotypic lead(II) analogue Pb2Te3O8 (Champarnaud-Mesjard et al., 2001 ▸) are reported.

Structural commentary

The asymmetric unit of Ca2Te3O8 comprises two Ca sites, four Te sites and eight O sites. One Ca site (Ca2) is located on Wyckoff position 8g (site symmetry ..m), sites Te1 on 4c (m2m), Te2 on 8f (m..), Te4 on 8g, O1 on 8f, O2 on 8e (2..) and O7 and O8 both on 8g; all other sites are on general positions 16h.

The two Ca2+ cations are surrounded by eight (Ca1) and nine (Ca2) O atoms, considering a cut-off value of 3.1 Å for relevant Ca—O distances (Table 1 ▸). The bond valence sums (Brown, 2002 ▸) computed with the parameters of Brown & Altermatt (1985 ▸) are 1.89 valence units (v.u.) for Ca1 and 2.02 v.u. for Ca2, in good agreement with the expected value of 2. Likewise, the mean Ca—O bond length of 2.55 Å for Ca1 and 2.57 Å for Ca2 are in accord with the values for eight- and nine-coordinate Ca of 2.50 (15) and 2.56 (20) Å, respectively (Gagné & Hawthorne, 2016 ▸). Whereas the [Ca1O8] polyhedron is difficult to derive from a simple geometric figure, [Ca2O9] can be best described as a monocapped square anti­prism (Fig. 1 ▸).

Table 1

Comparison of bond lengths (Å) in Ca2Te3O8 and isotypic Pb2Te3O8

	Ca2Te3O8 a	Pb2Te3O8 b
M1—O3i	2.3198 (11)	2.372 (8)
M1—O6ii	2.3903 (13)	2.440 (8)
M1—O5	2.3924 (11)	2.470 (6)
M1—O3	2.4691 (12)	2.636 (8)
M1—O5iii	2.4712 (11)	2.934 (8)
M1—O3iv	2.6212 (12)	3.032 (8)
M1—O4	2.7186 (13)
M1—O8	3.0360 (4)	3.069 (2)
M2—O8v	2.3089 (18)	2.439 (9)
M2—O7vi	2.3660 (17)	2.374 (10)
M2—O5v	2.4497 (11)	2.556 (6)
M2—O5iii	2.4497 (11)	2.556 (6)
M2—O8	2.4749 (19)	3.080 (11)
M2—O4vi	2.6335 (13)	2.732 (6)
M2—O4iv	2.6335 (13)	2.732 (6)
M2—O4	2.9154 (13)	3.342 (7)
M2—O4ii	2.9154 (13)	3.342 (7)
Te1—O7vii	1.8369 (17)	1.852 (10)
Te1—O7viii	1.8369 (17)	1.852 (10)
Te1—O1	2.1608 (17)	2.160 (9)
Te1—O1ii	2.1608 (17)	2.160 (9)
Te2—O6ix	1.8522 (12)	1.859 (8)
Te2—O6	1.8522 (12)	1.859 (8)
Te2—O1	1.8902 (17)	1.883 (10)
Te3—O3	1.8602 (11)	1.868 (8)
Te3—O5x	1.8743 (10)	1.856 (7)
Te3—O2x	2.0123 (5)	2.008 (3)
Te3—O4	2.3222 (12)	2.338 (6)
Te4—O8	1.8694 (17)	1.857 (10)
Te4—O4	1.8994 (11)	1.900 (7)
Te4—O4ii	1.8994 (11)	1.900 (7)

Notes: (a) this study; (b) Champarnaud-Mesjard et al. (2001 ▸); single-crystal data with a = 19.522 (4), b = 7.121 (1) and c = 18.813 (4) Å. Symmetry codes: (i) x, −y + 1, −z + 1; (ii) x, y, −z + ; (iii) −x + , y + , z; (iv) −x + , y − , z; (v) −x + , y + , −z + ; (vi) −x + , y − , −z + ; (vii) x, y − 1, z; (viii) −x + 1, y − 1, −z + ; (ix) −x + 1, y, z; (x) x, y + 1, z.

Figure 1

(a) The [Ca1O8] and (b) the [Ca1O9] polyhedra in the crystal structure of Ca2Te3O8. Displacement ellipsoids are drawn at the 90% probability level. Symmetry codes refer to Table 1 ▸.

All four Te atoms have an oxidation state of +IV and can be divided into two pairs with the most commonly observed three-coordination in the form of a trigonal pyramid (Te2 and Te4) and four-coordination in the form of a bis­phenoid (Te1 and Te3). The Te—O bond lengths within the [TeO3] trigonal pyramids are only slightly spread, ranging from 1.8522 (12) to 1.8994 (11) Å. The two [TeO4] bis­phenoids are characterised by two short bonds of < 2 Å and two longer bonds of > 2 Å, with the maximum at 2.3222 (12) Å for Te3. All Te—O bond lengths (Table 1 ▸) are in characteristic ranges for oxotellurates(IV) with three- and four-coordinate tellurium, as reviewed recently by Christy et al. (2016 ▸).

Bond valence sums for the four Te atoms computed with the parameters of Brese and O’Keeffe (1991 ▸) are 4.14, 4.07, 3.99 and 3.81 v.u., but are considerably lower when the revised parameters of Mills & Christy (2013 ▸) are used, i.e. 3.93, 3.80, 3.81 and 3.57 v.u.

The oxotellurium(IV) network is built up from two different anions, both with composition [Te3O8]4−. One anion is made up from an infinite zigzag chain that extends parallel to [001] and consists of a pair of corner-sharing [Te3O4] bis­phenoids linked alternately to a [Te4O3] trigonal pyramid {= [(Te4O1/1O2/2)(Te3O2/1O2/2)2]} (Fig. 2 ▸ a). The second oxotellurate(IV) anion is finite and is situated between neighbouring chain anions. It is comprised of a curved [Te3O8]4− unit with a central Te1O4 bis­phenoid linked to two [Te2O3] trigonal pyramids {= [(Te1O2/1O1/2)2(Te2O2/2O2/1)]} (Fig. 2 ▸ b).

Figure 2

(a) The chain [Te3O8]4− anion and (b) the finite [Te3O8]4− anion in the crystal structure of Ca2Te3O8. Displacement ellipsoids are drawn at the 90% probability level. Symmetry codes refer to Table 1 ▸.

In the crystal, the two types of [Te3O8]4− anions are arranged in layers parallel to (100). Approximately at x ≃ 1/4 and 3/4, the calcium cations link adjacent layers into the three-dimensional framework (Fig. 3 ▸).

Figure 3

The crystal structure of Ca2Te3O8 in a projection along [00]. Displacement ellipsoids and colour code as in Figs. 1 ▸ and 2 ▸.

Ca2Te3O8 is isotypic with Pb2Te3O8 (Champarnaud-Mesjard et al., 2001 ▸), but not with its higher alkaline earth homologue Sr2Te3O8, which is reported to have a different ortho­rhom­bic cell, with details of the structure not known (Elerman & Koçak, 1986 ▸). Comparison of the bond lengths of the [MO] (M = Ca, Pb) polyhedra and the [TeO3] and [TeO4] units in the isotypic structures of Ca2Te3O8 and Pb2Te3O8 (Table 1 ▸) reveals nearly identical values for the individual oxotellurate(IV) units, but differences up to 0.6 Å for the metal–oxygen polyhedra. On one hand, this behaviour is ascribed to the different ionic radii for eight-coordinate CaII and PbII of 1.12 and 1.29 Å, respectively (Shannon, 1976 ▸), and, on the other hand, to the stereochemical activity (Galy et al., 1975 ▸) of the 6s 2 free-electron lone pair located at PbII that is responsible for the formation of off-centred lead–oxygen polyhedra with either holo- or hemidirected oxygen ligands (Shimoni-Livny et al., 1998 ▸).

For a qu­anti­tative structural comparison of the isotypic M 2Te3O8 (M = Ca, Pb) structures, the program compstru (de la Flor et al., 2016 ▸), available at the Bilbao Crystallographic Server (Aroyo et al., 2006 ▸), was used. The degree of lattice distortion is 0.0205, the maximum distance between the atomic positions of paired atoms is 0.403 Å for pair O8, the arithmetic mean of all distances is 0.195 Å and the measure of similarity is 0.05.

Synthesis and crystallization

Crystals of Ca2Te3O8 were obtained as one of the products from a flux synthesis using a CsCl/NaCl salt mixture (molar ratio 0.65/0.35). To 1.5 g of the salt mixture were added CaO (0.075 g; freshly prepared by heating CaCO3 at 1473 K for 1 d) and TeO2 (0.425 g) according to a molar ratio of 1:2. The reaction mixture was placed in a silica ampoule that was subsequently evacuated and sealed. The ampoule was placed vertically in a furnace and heated from room temperature within 3 h to 793 K, kept at that temperature for 90 h and cooled within 10 h to room temperature. The silica ampoule was broken and the solidified melt leached out with water for two h. The colourless product was filtered off, washed with water and was dried in a stream of air. The title compound was present in the form of a few crystals that were distinguishable from the other crystals due to their characteristic square form (maximum edge length 1.5 mm). Other phases identified by single-crystal X-ray diffraction measurements of selected crystals and by powder X-ray diffraction measurements of the bulk were CaTe2O5 in the mica-like modification reported by Redman et al. (1970 ▸) as the main phase (tiny colourless plates) and Ca4Te5O14 (small colourless pinacoids; Weil, 2004 ▸).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. Starting coordinates for the refinement were taken from isotypic Pb2Te3O8 (Champarnaud-Mesjard et al., 2001 ▸). Both remaining maximum and minimum electron-density peaks are located 0.64 and 0.30 Å from the Te2 site.

Table 2

Experimental details

Crystal data
Chemical formula	Ca2Te3O8
M r	590.95
Crystal system, space group	Orthorhombic, C m c m
Temperature (K)	297
a, b, c (Å)	18.7368 (15), 6.8399 (6), 18.5652 (15)
V (Å3)	2379.3 (3)
Z	12
Radiation type	Mo Kα
μ (mm−1)	12.27
Crystal size (mm)	0.25 × 0.15 × 0.10
Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 ▸)
T min, T max	0.472, 0.750
No. of measured, independent and observed [I > 2σ(I)] reflections	47523, 6097, 5325
R int	0.043
(sin θ/λ)max (Å−1)	1.057
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.023, 0.043, 1.12
No. of reflections	6097
No. of parameters	101
Δρmax, Δρmin (e Å−3)	4.13, −2.08

Computer programs: APEX3 and SAINT (Bruker, 2016 ▸), SHELXL2017 (Sheldrick, 2015 ▸), ATOMS (Dowty, 2006 ▸) and publCIF (Westrip, 2010 ▸). Starting coordinates taken from an isotypic compound.

Crystal structure: contains datablock(s) I, general. DOI: 10.1107/S2056989018017310/pk2611sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989018017310/pk2611Isup2.hkl

CCDC reference: 1883382

Additional supporting information: crystallographic information; 3D view; checkCIF report

Ca2Te3O8	Dx = 4.949 Mg m−3
Mr = 590.95	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Cmcm	Cell parameters from 9248 reflections
a = 18.7368 (15) Å	θ = 3.2–48.6°
b = 6.8399 (6) Å	µ = 12.27 mm−1
c = 18.5652 (15) Å	T = 297 K
V = 2379.3 (3) Å3	Plate, colourless
Z = 12	0.25 × 0.15 × 0.10 mm
F(000) = 3120

Bruker APEXII CCD diffractometer	5325 reflections with I > 2σ(I)
ω scans	Rint = 0.043
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	θmax = 48.7°, θmin = 2.2°
Tmin = 0.472, Tmax = 0.750	h = −37→39
47523 measured reflections	k = −14→14
6097 independent reflections	l = −36→39

Refinement on F2	Primary atom site location: isomorphous structure methods
Least-squares matrix: full	w = 1/[σ2(Fo2) + (0.0102P)2 + 6.3377P] where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.023	(Δ/σ)max = 0.002
wR(F2) = 0.043	Δρmax = 4.13 e Å−3
S = 1.12	Δρmin = −2.08 e Å−3
6097 reflections	Extinction correction: SHELXL2017 (Sheldrick, 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
101 parameters	Extinction coefficient: 0.00143 (3)
0 restraints

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.

	x	y	z	Uiso*/Ueq
Ca1	0.29994 (2)	0.36584 (4)	0.41210 (2)	0.00884 (4)
Ca2	0.19996 (2)	0.49754 (6)	0.250000	0.00819 (5)
Te1	0.500000	0.08952 (3)	0.250000	0.00866 (3)
Te2	0.500000	0.29743 (2)	0.07448 (2)	0.00865 (2)
Te3	0.37898 (2)	0.84140 (2)	0.41362 (2)	0.00685 (2)
Te4	0.37986 (2)	0.54478 (2)	0.250000	0.00616 (2)
O1	0.500000	0.0728 (2)	0.13377 (9)	0.0150 (3)
O2	0.40826 (9)	0.000000	0.500000	0.0146 (3)
O3	0.31332 (6)	0.69421 (16)	0.46567 (6)	0.01057 (16)
O4	0.32340 (7)	0.67071 (18)	0.32118 (6)	0.01226 (17)
O5	0.31362 (6)	0.02866 (15)	0.38074 (6)	0.00918 (15)
O6	0.42263 (7)	0.42092 (19)	0.11674 (8)	0.0165 (2)
O7	0.42329 (9)	0.9223 (3)	0.250000	0.0135 (3)
O8	0.31736 (10)	0.3318 (3)	0.250000	0.0209 (4)

	U11	U22	U33	U12	U13	U23
Ca1	0.00841 (9)	0.00807 (9)	0.01005 (9)	0.00102 (7)	−0.00031 (7)	0.00024 (7)
Ca2	0.00857 (13)	0.00778 (12)	0.00821 (12)	0.00113 (10)	0.000	0.000
Te1	0.00648 (6)	0.00643 (6)	0.01305 (7)	0.000	0.000	0.000
Te2	0.00773 (4)	0.00848 (4)	0.00974 (4)	0.000	0.000	−0.00001 (3)
Te3	0.00550 (3)	0.00710 (3)	0.00794 (3)	0.00067 (2)	0.00072 (2)	0.00095 (2)
Te4	0.00569 (4)	0.00572 (4)	0.00706 (4)	0.00012 (3)	0.000	0.000
O1	0.0227 (8)	0.0108 (6)	0.0116 (6)	0.000	0.000	0.0018 (5)
O2	0.0110 (6)	0.0209 (7)	0.0119 (6)	0.000	0.000	−0.0089 (5)
O3	0.0123 (4)	0.0103 (4)	0.0091 (4)	−0.0023 (3)	0.0028 (3)	0.0010 (3)
O4	0.0122 (4)	0.0157 (4)	0.0088 (4)	0.0031 (3)	0.0022 (3)	−0.0022 (3)
O5	0.0096 (4)	0.0072 (3)	0.0107 (4)	0.0021 (3)	−0.0006 (3)	0.0000 (3)
O6	0.0091 (4)	0.0175 (5)	0.0228 (6)	0.0037 (4)	0.0000 (4)	−0.0049 (4)
O7	0.0072 (5)	0.0142 (6)	0.0193 (7)	−0.0022 (5)	0.000	0.000
O8	0.0099 (7)	0.0077 (6)	0.0451 (12)	−0.0030 (5)	0.000	0.000

Ca1—O3i	2.3198 (11)	Ca2—O4	2.9154 (13)
Ca1—O6ii	2.3903 (13)	Ca2—O4ii	2.9154 (13)
Ca1—O5	2.3924 (11)	Ca2—Te4	3.3863 (5)
Ca1—O3	2.4691 (12)	Ca2—Te4vi	3.4390 (5)
Ca1—O5iii	2.4712 (11)	Ca2—Te3vi	3.5434 (3)
Ca1—O3iv	2.6212 (12)	Te1—O7vii	1.8369 (17)
Ca1—O4	2.7186 (13)	Te1—O7viii	1.8369 (17)
Ca1—O8	3.0360 (4)	Te1—O1	2.1608 (17)
Ca1—Te3iv	3.3567 (4)	Te1—O1ii	2.1609 (17)
Ca1—Te3	3.5742 (4)	Te2—O6ix	1.8522 (12)
Ca1—Te4	3.5773 (4)	Te2—O6	1.8522 (12)
Ca1—Ca2	3.6575 (4)	Te2—O1	1.8902 (17)
Ca2—O8v	2.3089 (18)	Te3—O3	1.8602 (11)
Ca2—O7vi	2.3660 (17)	Te3—O5x	1.8743 (10)
Ca2—O5v	2.4497 (11)	Te3—O2x	2.0123 (5)
Ca2—O5iii	2.4497 (11)	Te3—O4	2.3222 (12)
Ca2—O8	2.4749 (19)	Te4—O8	1.8694 (17)
Ca2—O4vi	2.6335 (13)	Te4—O4	1.8994 (11)
Ca2—O4iv	2.6335 (13)	Te4—O4ii	1.8994 (11)
O3i—Ca1—O6ii	98.22 (5)	O8v—Ca2—Te3vi	103.87 (2)
O3i—Ca1—O5	93.20 (4)	O7vi—Ca2—Te3vi	61.771 (12)
O6ii—Ca1—O5	89.68 (4)	O5v—Ca2—Te3vi	29.94 (2)
O3i—Ca1—O3	75.88 (4)	O5iii—Ca2—Te3vi	146.33 (3)
O6ii—Ca1—O3	81.32 (4)	O8—Ca2—Te3vi	103.47 (2)
O5—Ca1—O3	164.59 (4)	O4vi—Ca2—Te3vi	40.94 (3)
O3i—Ca1—O5iii	113.79 (4)	O4iv—Ca2—Te3vi	96.03 (3)
O6ii—Ca1—O5iii	134.77 (4)	O4—Ca2—Te3vi	147.38 (2)
O5—Ca1—O5iii	117.99 (4)	O4ii—Ca2—Te3vi	93.73 (2)
O3—Ca1—O5iii	76.84 (4)	Te4—Ca2—Te3vi	116.377 (7)
O3i—Ca1—O3iv	68.72 (4)	Te4vi—Ca2—Te3vi	63.068 (6)
O6ii—Ca1—O3iv	159.11 (4)	O7vii—Te1—O7viii	102.97 (11)
O5—Ca1—O3iv	75.37 (4)	O7vii—Te1—O1	88.11 (3)
O3—Ca1—O3iv	109.69 (4)	O7viii—Te1—O1	88.11 (3)
O5iii—Ca1—O3iv	66.05 (4)	O7vii—Te1—O1ii	88.11 (3)
O3i—Ca1—O4	136.52 (4)	O7viii—Te1—O1ii	88.11 (3)
O6ii—Ca1—O4	65.45 (4)	O1—Te1—O1ii	173.92 (9)
O5—Ca1—O4	124.82 (4)	O7vii—Te1—Ca2vi	28.98 (5)
O3—Ca1—O4	62.35 (4)	O7viii—Te1—Ca2vi	131.95 (6)
O5iii—Ca1—O4	69.34 (4)	O1—Te1—Ca2vi	89.497 (8)
O3iv—Ca1—O4	135.24 (4)	O1ii—Te1—Ca2vi	89.497 (8)
O3i—Ca1—O8	160.81 (5)	O7vii—Te1—Ca2xi	131.95 (6)
O6ii—Ca1—O8	71.74 (5)	O7viii—Te1—Ca2xi	28.98 (5)
O5—Ca1—O8	70.93 (4)	O1—Te1—Ca2xi	89.497 (8)
O3—Ca1—O8	117.27 (4)	O1ii—Te1—Ca2xi	89.497 (8)
O5iii—Ca1—O8	83.89 (4)	Ca2vi—Te1—Ca2xi	160.934 (13)
O3iv—Ca1—O8	115.39 (4)	O6ix—Te2—O6	103.01 (8)
O4—Ca1—O8	54.98 (4)	O6ix—Te2—O1	97.12 (6)
O3i—Ca1—Te3iv	95.22 (3)	O6—Te2—O1	97.12 (6)
O6ii—Ca1—Te3iv	165.99 (3)	O6ix—Te2—Ca1xii	30.77 (4)
O5—Ca1—Te3iv	93.50 (3)	O6—Te2—Ca1xii	133.69 (4)
O3—Ca1—Te3iv	98.24 (3)	O1—Te2—Ca1xii	93.563 (8)
O5iii—Ca1—Te3iv	33.33 (2)	O6ix—Te2—Ca1ii	133.69 (4)
O3iv—Ca1—Te3iv	33.48 (2)	O6—Te2—Ca1ii	30.77 (4)
O4—Ca1—Te3iv	101.83 (3)	O1—Te2—Ca1ii	93.563 (8)
O8—Ca1—Te3iv	96.42 (4)	Ca1xii—Te2—Ca1ii	163.902 (10)
O3i—Ca1—Te3	96.23 (3)	O3—Te3—O5x	96.14 (5)
O6ii—Ca1—Te3	57.30 (3)	O3—Te3—O2x	93.33 (5)
O5—Ca1—Te3	146.60 (3)	O5x—Te3—O2x	93.97 (5)
O3—Ca1—Te3	29.18 (3)	O3—Te3—O4	79.35 (5)
O5iii—Ca1—Te3	87.05 (3)	O5x—Te3—O4	79.04 (5)
O3iv—Ca1—Te3	137.74 (3)	O2x—Te3—O4	169.18 (6)
O4—Ca1—Te3	40.52 (3)	O3—Te3—Ca1iii	51.01 (4)
O8—Ca1—Te3	91.90 (3)	O5x—Te3—Ca1iii	46.42 (3)
Te3iv—Ca1—Te3	117.328 (9)	O2x—Te3—Ca1iii	104.60 (5)
O3i—Ca1—Te4	146.96 (3)	O4—Te3—Ca1iii	64.59 (3)
O6ii—Ca1—Te4	49.84 (3)	O3—Te3—Ca2v	109.41 (4)
O5—Ca1—Te4	94.60 (3)	O5x—Te3—Ca2v	40.72 (3)
O3—Ca1—Te4	89.14 (3)	O2x—Te3—Ca2v	129.382 (18)
O5iii—Ca1—Te4	90.46 (3)	O4—Te3—Ca2v	47.99 (3)
O3iv—Ca1—Te4	144.22 (3)	Ca1iii—Te3—Ca2v	63.955 (8)
O4—Ca1—Te4	31.52 (2)	O3—Te3—Ca1	40.32 (4)
O8—Ca1—Te4	31.50 (3)	O5x—Te3—Ca1	110.40 (3)
Te3iv—Ca1—Te4	116.244 (9)	O2x—Te3—Ca1	127.580 (17)
Te3—Ca1—Te4	61.433 (6)	O4—Te3—Ca1	49.52 (3)
O3i—Ca1—Ca2	154.68 (3)	Ca1iii—Te3—Ca1	68.372 (6)
O6ii—Ca1—Ca2	105.63 (3)	Ca2v—Te3—Ca1	95.427 (9)
O5—Ca1—Ca2	95.28 (3)	O3—Te3—Ca1i	26.53 (4)
O3—Ca1—Ca2	99.17 (3)	O5x—Te3—Ca1i	105.99 (3)
O5iii—Ca1—Ca2	41.77 (3)	O2x—Te3—Ca1i	68.39 (3)
O3iv—Ca1—Ca2	90.45 (3)	O4—Te3—Ca1i	105.36 (3)
O4—Ca1—Ca2	51.91 (3)	Ca1iii—Te3—Ca1i	68.861 (8)
O8—Ca1—Ca2	42.13 (4)	Ca2v—Te3—Ca1i	132.402 (9)
Te3iv—Ca1—Ca2	60.505 (8)	Ca1—Te3—Ca1i	60.638 (8)
Te3—Ca1—Ca2	89.690 (9)	O8—Te4—O4	90.26 (6)
Te4—Ca1—Ca2	55.803 (9)	O8—Te4—O4ii	90.26 (6)
O8v—Ca2—O7vi	94.49 (6)	O4—Te4—O4ii	88.18 (7)
O8v—Ca2—O5v	84.22 (3)	O8—Te4—Ca2	45.74 (6)
O7vi—Ca2—O5v	85.27 (3)	O4—Te4—Ca2	59.26 (4)
O8v—Ca2—O5iii	84.22 (3)	O4ii—Te4—Ca2	59.26 (4)
O7vi—Ca2—O5iii	85.27 (3)	O8—Te4—Ca2v	115.43 (6)
O5v—Ca2—O5iii	164.44 (5)	O4—Te4—Ca2v	49.41 (4)
O8v—Ca2—O8	125.35 (5)	O4ii—Te4—Ca2v	49.42 (4)
O7vi—Ca2—O8	140.16 (6)	Ca2—Te4—Ca2v	69.699 (8)
O5v—Ca2—O8	97.59 (3)	O8—Te4—Ca1	58.067 (9)
O5iii—Ca2—O8	97.59 (3)	O4—Te4—Ca1	48.45 (4)
O8v—Ca2—O4vi	144.79 (4)	O4ii—Te4—Ca1	120.49 (4)
O7vi—Ca2—O4vi	69.70 (5)	Ca2—Te4—Ca1	63.297 (6)
O5v—Ca2—O4vi	63.85 (3)	Ca2v—Te4—Ca1	97.242 (7)
O5iii—Ca2—O4vi	123.62 (4)	O8—Te4—Ca1ii	58.067 (9)
O8—Ca2—O4vi	76.04 (5)	O4—Te4—Ca1ii	120.49 (4)
O8v—Ca2—O4iv	144.79 (4)	O4ii—Te4—Ca1ii	48.45 (4)
O7vi—Ca2—O4iv	69.70 (5)	Ca2—Te4—Ca1ii	63.299 (6)
O5v—Ca2—O4iv	123.62 (4)	Ca2v—Te4—Ca1ii	97.242 (7)
O5iii—Ca2—O4iv	63.85 (3)	Ca1—Te4—Ca1ii	114.545 (11)
O8—Ca2—O4iv	76.04 (5)	Te2—O1—Te1	122.58 (9)
O4vi—Ca2—O4iv	60.24 (5)	Te3vii—O2—Te3i	148.36 (9)
O8v—Ca2—O4	73.10 (5)	Te3—O3—Ca1i	132.49 (6)
O7vi—Ca2—O4	149.63 (3)	Te3—O3—Ca1	110.51 (5)
O5v—Ca2—O4	119.75 (4)	Ca1i—O3—Ca1	102.82 (4)
O5iii—Ca2—O4	66.29 (3)	Te3—O3—Ca1iii	95.51 (5)
O8—Ca2—O4	58.73 (4)	Ca1i—O3—Ca1iii	111.28 (4)
O4vi—Ca2—O4	134.77 (3)	Ca1—O3—Ca1iii	99.92 (4)
O4iv—Ca2—O4	104.43 (4)	Te4—O4—Te3	119.50 (6)
O8v—Ca2—O4ii	73.10 (5)	Te4—O4—Ca2v	97.37 (5)
O7vi—Ca2—O4ii	149.63 (3)	Te3—O4—Ca2v	91.07 (4)
O5v—Ca2—O4ii	66.29 (3)	Te4—O4—Ca1	100.03 (5)
O5iii—Ca2—O4ii	119.75 (4)	Te3—O4—Ca1	89.96 (4)
O8—Ca2—O4ii	58.73 (4)	Ca2v—O4—Ca1	159.36 (5)
O4vi—Ca2—O4ii	104.43 (4)	Te4—O4—Ca2	86.69 (4)
O4iv—Ca2—O4ii	134.77 (3)	Te3—O4—Ca2	153.51 (5)
O4—Ca2—O4ii	53.91 (5)	Ca2v—O4—Ca2	89.17 (4)
O8v—Ca2—Te4	92.60 (5)	Ca1—O4—Ca2	80.88 (3)
O7vi—Ca2—Te4	172.91 (4)	Te3vii—O5—Ca1	130.51 (5)
O5v—Ca2—Te4	95.46 (3)	Te3vii—O5—Ca2vi	109.34 (5)
O5iii—Ca2—Te4	95.46 (3)	Ca1—O5—Ca2vi	108.29 (4)
O8—Ca2—Te4	32.75 (4)	Te3vii—O5—Ca1iv	100.25 (5)
O4vi—Ca2—Te4	104.27 (3)	Ca1—O5—Ca1iv	106.55 (4)
O4iv—Ca2—Te4	104.27 (3)	Ca2vi—O5—Ca1iv	96.02 (4)
O4—Ca2—Te4	34.05 (2)	Te2—O6—Ca1ii	125.87 (7)
O4ii—Ca2—Te4	34.05 (2)	Te1x—O7—Ca2v	128.92 (9)
O8v—Ca2—Te4vi	146.15 (5)	Te4—O8—Ca2vi	149.29 (10)
O7vi—Ca2—Te4vi	51.66 (4)	Te4—O8—Ca2	101.52 (8)
O5v—Ca2—Te4vi	91.90 (3)	Ca2vi—O8—Ca2	109.19 (7)
O5iii—Ca2—Te4vi	91.90 (3)	Te4—O8—Ca1	90.43 (3)
O8—Ca2—Te4vi	88.51 (4)	Ca2vi—O8—Ca1	93.49 (3)
O4vi—Ca2—Te4vi	33.21 (2)	Ca2—O8—Ca1	82.49 (4)
O4iv—Ca2—Te4vi	33.21 (2)	Te4—O8—Ca1ii	90.43 (3)
O4—Ca2—Te4vi	135.31 (3)	Ca2vi—O8—Ca1ii	93.49 (3)
O4ii—Ca2—Te4vi	135.31 (3)	Ca2—O8—Ca1ii	82.49 (4)
Te4—Ca2—Te4vi	121.252 (12)	Ca1—O8—Ca1ii	164.82 (7)