Na₇Al₃(As₂O₇)₄

The title compound, hepta­sodium trialuminium tetrakis(diarsenate), has been isolated as single crystals from a solid-state reaction. Its structure, which is isotypic with that of the Na₇Fe₃(X₂O₇)₄ (X = As, P) family of compounds, consists of AlO₆ octa­hedra sharing their vertices with As₂O₇ groups, forming a three-dimensional [Al₃(As₂O₇)₄]_∞ framework incorporating channels occupied by the sodium ions. One of the aluminium ions lies on a crystallographic twofold axis. The sodium ions are situated over ten positions (one with site symmetry 2), all but one of which are partially occupied.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](Al-O) = 0.004 Å
• Disorder in solvent or counterion
• R factor = 0.034
• wR factor = 0.085
• Data-to-parameter ratio = 11.7

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT202_ALERT_3_C Isotropic non-H Atoms in Anion/Solvent .........          1
PLAT906_ALERT_3_C Large K value in the Analysis of Variance ......      3.142
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          1
PLAT934_ALERT_3_C Number of (Iobs-Icalc)/SigmaW > 10 Outliers ....          1
PLAT976_ALERT_2_C Negative Residual Density at 0.89A from O11    .      -0.60 eA-3

Alert level G
PLAT004_ALERT_5_G Info: Polymeric Structure Found with Dimension .          2
PLAT005_ALERT_5_G No _iucr_refine_instructions_details  in the CIF          ? Do !
PLAT042_ALERT_1_G Calc. and Reported MoietyFormula Strings  Differ          ? Check
PLAT083_ALERT_2_G SHELXL Second Parameter in WGHT Unusually Large.      24.91
PLAT302_ALERT_4_G Note: Anion/Solvent Disorder ...................         73 %
PLAT811_ALERT_5_G No ADDSYM Analysis: Too Many Excluded Atoms ....          ! Info
PLAT912_ALERT_4_G Missing # of FCF Reflections Above STh/L=  0.600          4
PLAT961_ALERT_5_G Dataset Contains no Negative Intensities .......          ! Check

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   5 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   8 ALERT level G = General information/check it is not something unexpected

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 ALERT type 2 Indicator that the structure model may be wrong or deficient
   4 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion
   4 ALERT type 5 Informative message, check

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S1. Comment

A new family of compounds Na₇M₃(X₂O₇)₄ (M = Fe, Al, Cr, Ga; X = P, As) studied by Masquelier et al. (1994) present interesting ion conductivity properties. In this family line, a structural study was carried out only for Na₇Fe₃(As₂O₇)₄ and Na₇Fe₃(P₂O₇)₄ compounds by Masquelier et al.(1990, 1991). In addition, another structural study was conducted to isotypes compounds Na₅Ag₂Fe₃(As₂O₇)₄ and Na₂Ag₅Fe₃(P₂O₇)₄ by Quarez et al. (2009). Also, electrical measurements were also made by Quarez et al. (2009) for Ag₇Fe₃(X₂O₇)₄ (X = As, P) compounds. However, as for the Na₇Al₃(As₂O₇)₄ compound no structural analysis has been reported so far.

The structure of compound Na₇Al₃(As₂O₇)₄ shows a three-dimensional anionic framework [Al₃(As₂O₇) ₄]_∞ composed of octahedron AlO₆ sharing vertices with As₂O₇ groups. This framework defines the interstitial spaces in which the Na ⁺ ions are located in a partially disordered distribution to ensure the electrical neutrality. The single unit [Al₃(As₂O₇)₄]^7- consists of an octahedron Al1O₆ and two octahedra Al2O₆ related to As₂O₇ group by sharing vertices (Fig. 1). The two aluminium atoms occupy two crystallographically independent sites: the aluminium Al1 is in special position 4e of a symmetry equal to 2; whereas the Al2 is in general position of 8f. In this unit, the connection between the octahedra Al1O₆ and Al2O₆ is provided by the group As1As2O₇ through oxygen atom O14. In this structure, the units [Al₃(As₂O₇)₄]^7- are inter-related thanks to composite bridges of types Al—O—As and As—O—Al respectively. These bridges are located between the octahedra AlO₆ and As₂O₇ diarsenates groups in order to handle two types of parallel layers to the (a, b) plan. According to (010) (Fig. 2), a projection of the structure shows that the anionic framework consists of a succession of layers as follow: A: [Al1(As2As3O₇)₂]_∞ and B: [(Al2As3As4O₇)₂]_∞ perpendicular to c alternately. In the layers A, the only components are Octahedra Al1O₆, whereas other aluminium octahedra Al2O₆ shape layers B.

On the one hand, in the layer A, each octahedron Al1O₆ is connected to two groups As1As2O₇ by sharing both a vertex and two other groups As1As2O₇ such as the Al1O₆ octahedron shares two of its vertices with the same group As₂O₇. By rotation around the fold axis, these groups are equivalent (Fig. 3). This mode of connection is found in phosphates: ARu₂(P₂O₇)₂ (A = Li, Na, Ag) (Fukuoka et al., 2003.), NaMo₂(P₂O₇)₂ (Hwu et al., 1991), and SrV₂(P₂O₇)₂ (Lii et al., 1989).

On the other hand, in the layer B, each octahedron Al2O₆ is connected to four As₂O₇ groups through the formation of composite bridges Al—O—As and the division of two vertices with a fifth group As₂O₇ (Fig. 3). This layer is formed by AlAs₂O₁₁ units related through the formation of Al—O—As composed bridges. This type of M—O—As bond between MAs₂O₁₁ units (M = Al, Ga, Fe) is situated in the following isostructural compounds: RbAlAs₂O₇ (Boughzala et al., 1993), KAlAs₂O₇ (Boughzala et al., 1995), KGaAs₂O₇ (Lin et al., 1996) and TlFe_0.22Al_0.78As₂O₇ (Ouerfelli et al., 2007).

The O14 oxygen atom guarantees the bond between the layers A and B through the bridges Al2—O14—As2.

The anionic framework [Al₃(As₂O₇)₄]_∞ can be also described as alternate stacking of octahedral AlO₆ layers and As₂O₇ groups layers parallel to (101) (Fig. 4).

In this structure, the sodium ions are distributed through ten crystallographic sites in the interstices of the anionic network. The first type of the site corresponding to 8f position is totally occupied by the Na1 cation which is localized in the layer B. As for the nine other sites, they are partially occupied. And these can be arranged into groups of three sets: (Na2A—Na2B—Na2C), (Na3A—Na3B) and (Na4A—Na4B—Na4C—Na4D). Different sites of the same group are too close to be occupied simultaneously. As a result, the total number of Na⁺ ions for each group is less than or equal to one. These sodium ions are predominantly located in the layer A and they are distributed in the vicinity of two plans parallel to (001) respectively to dimensions z ≈ 0.15 and z ≈ 0.35. Also, the Na2B site, located on the binary axis, occupies an intermediate position (z = 1/4). Examination of geometric factors in the structure shows that they are in accordance with those found in the literature (Driss et al., 1994; Masquelier et al., 1995.). In addition, the use of the BVS method for the calculation of different valences of bonds, using the empirical formula of Brown (Brown & Altermatt, 1985), does satisfy the expected values of ion charge: Al1 (2.73), Al2 (2.69), As1 (4.90), As2 (4.98), As3 (5.01), As4 (5.00), Na1 (1.16), Na2A (0.87), Na2B (1.13), Na2C (0.79), Na3A (1.00), Na3B (1.03), Na4A (0.97), Na4B (0.95), Na4C (1.01), Na4D (0, 93). In order to use these structural data and to connect them to the physicochemical properties, especially ion-conducting electrical measurements through a complex impedance bridge are in progress.

Related literature

For isotopic compounds, see: Masquelier & D'Yvoire (1991); Masquelier et al. (1990, 1994); Quarez et al.(2009, 2010). For bond lengths and angles in related structures, see: Driss & Jouini (1994); Masquelier et al. (1995). For structural relationships, see: Lii et al. (1989); Hwu & Willis (1991); Boughzala et al. (1993); Boughzala & Jouini (1995); Lin & Lii (1996); Fukuoka et al. (2003); Ouerfelli et al. (2007). For bond-valence parameters, see: Brown & Altermatt (1985).

S2. Experimental

The crystals related to the Na₇Al₃ (As₂O₇)₄ phase were obtained from reactants: NaHCO₃ (Prolabo, 27778), Al₂O₃ (Riedel-de Haen, 167305) NH₄H₂AsO₄ (prepared in the laboratory, JCPDS-775), taken in molar proportions: Na: A l: As = 10: 1: 9. Finely ground, the mixture was put in a porcelain crucible, placed in an oven and preheated in air at 673 K for 24 h to remove volatiles. After that, the mixture is raised to a synthesis temperature close to the melting 968 K through stages of 100 degrees followed by grinding. The mixture is then left at this temperature for a week to promote germination and growth of crystals. The final residue undergoes a first slow cooling (5 ° / half day, at 800 K) and a second fast (50 ° / h) to room temperature. Transparent crystals of prismatic form, clear outline and sufficient size for measurements of intensities, have been separated from the stream by successive hot water washes.

S3. Refinement

The collection was carried out in the monoclinic system of C2 / c space group. During the final refinement and for electrical neutrality reasons, the occupancy rate of Na⁺ cations were conducted using the SUMP condition authorized by the SHELXL program. The refinement of all variable parameters leads to well defined ellipsoids. The maximum and minimum densities of electrons remaining in the Fourier-difference are respectively situated at 0.86 Å from the As4 site and at 1.35 Å from the NA3B site.

Computing details

Data collection: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992); cell refinement: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1998); software used to prepare material for publication: WinGX (Farrugia, 2012).

Figures

	Fig. 1. Part of Na7Al3 (As2O7) 4 structure. The ellipsoids were defined with 50% probability. [Symmetry code: (i): - x, y, - z + 0.5; (ii): x - 1/2, y - 1/2, z; (iii): - x + 1/2, y - 1/2, - z + 0.5; (iv): - x + 1, - y, - z + 1; (v): -x + 1/2, - y + 1/2, - z + 1].
	Fig. 2. Projection of Na7Al3(As2O7)4 structure along [010]. The Na sites are numbered. The picture indicates the location of the A and B layers and the π planes at z ≈ 0.15 and 0.35.
	Fig. 3. Arrangement of Al1O6 octahedra and As1As2O7 groups in the A-layer and arrangement of Al2O6 octahedra and As3As4O7 groups in the B-layer.
	Fig. 4. Alternate stacking of octahedral AlO6 layers and As2O7 groups layers parallel to (-101).

Heptasodium trialuminium tetrakis(diarsenate)

Crystal data

Na7Al3(As2O7)4	F(000) = 2416
Mr = 1289.23	Dx = 3.613 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 25 reflections
a = 9.800 (1) Å	θ = 10–15°
b = 8.468 (1) Å	µ = 11.50 mm^−1
c = 28.637 (2) Å	T = 298 K
β = 94.14 (1)°	Parallelipiped, colorless
V = 2370.3 (4) Å^3	0.25 × 0.20 × 0.1 mm
Z = 4

Data collection

Enraf–Nonius CAD-4 diffractometer	2150 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.056
Graphite monochromator	θmax = 27.0°, θmin = 2.9°
ω/2θ scans	h = −12→3
Absorption correction: ψ scan (North et al., 1968)	k = −1→10
Tmin = 0.759, Tmax = 0.891	l = −36→36
3958 measured reflections	2 standard reflections every 120 min
2583 independent reflections	intensity decay: 1.1%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.034	w = 1/[σ^2(Fo^2) + (0.0314P)^2 + 24.9095P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.085	(Δ/σ)max = 0.001
S = 1.10	Δρmax = 1.27 e Å^−3
2583 reflections	Δρmin = −0.98 e Å^−3
221 parameters	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.00057 (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.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
Al1	0.0000	0.1057 (3)	0.2500	0.0082 (4)
Al2	0.31736 (15)	−0.02622 (18)	0.43636 (5)	0.0069 (3)
As1	0.30056 (5)	0.28137 (6)	0.246216 (18)	0.00898 (15)
As2	0.21753 (5)	0.15080 (6)	0.338657 (18)	0.00927 (15)
As3	0.58680 (5)	0.20071 (6)	0.464306 (18)	0.00733 (14)
As4	0.48861 (5)	0.34009 (6)	0.557696 (18)	0.00774 (14)
O1	0.3645 (4)	0.4537 (5)	0.26651 (14)	0.0149 (8)
O2	0.3734 (4)	0.2071 (5)	0.20087 (13)	0.0149 (8)
O3	0.1281 (4)	0.2823 (5)	0.23865 (14)	0.0148 (8)
O4	0.3327 (4)	0.1491 (4)	0.29386 (13)	0.0119 (8)
O5	0.4404 (4)	0.1537 (5)	0.43395 (15)	0.0170 (9)
O6	0.6943 (4)	0.2857 (5)	0.42888 (14)	0.0145 (8)
O7	0.6569 (4)	0.0529 (4)	0.49622 (13)	0.0120 (8)
O8	0.5686 (4)	0.4760 (5)	0.59037 (13)	0.0148 (8)
O9	0.3192 (4)	0.3690 (5)	0.54893 (14)	0.0142 (8)
O10	0.5262 (4)	0.1554 (4)	0.57538 (14)	0.0133 (8)
O11	0.5459 (4)	0.3542 (4)	0.50101 (13)	0.0139 (8)
O12	0.0599 (4)	0.1063 (5)	0.31482 (14)	0.0162 (8)
O13	0.2283 (5)	0.3289 (5)	0.36098 (15)	0.0210 (9)
O14	0.2752 (4)	−0.0052 (5)	0.37014 (13)	0.0162 (8)
Na1	−0.2221 (3)	−0.1225 (3)	0.44633 (9)	0.0249 (6)
Na2A	0.5268 (10)	−0.0466 (12)	0.3075 (4)	0.017 (2)*	0.24
Na2B	0.5000	0.0010 (13)	0.2500	0.013 (2)*	0.28
Na2C	0.5094 (8)	−0.0556 (10)	0.3269 (3)	0.0236 (18)*	0.32
Na3A	0.0283 (5)	−0.1551 (6)	0.35860 (17)	0.0186 (11)*	0.58
Na3B	−0.0112 (8)	−0.1372 (9)	0.3504 (3)	0.0118 (16)*	0.33
Na4A	−0.233 (2)	0.100 (3)	0.3543 (7)	0.016 (4)*	0.13
Na4B	−0.1483 (11)	0.2292 (14)	0.3505 (3)	0.024 (2)*	0.27
Na4C	−0.1939 (9)	0.0862 (10)	0.3420 (3)	0.0220 (17)*	0.35
Na4D	−0.184 (2)	0.175 (3)	0.3538 (7)	0.025 (4)*	0.14

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Al1	0.0067 (9)	0.0083 (10)	0.0094 (10)	0.000	0.0000 (8)	0.000
Al2	0.0071 (7)	0.0064 (7)	0.0072 (7)	0.0000 (6)	−0.0004 (5)	0.0007 (6)
As1	0.0065 (2)	0.0108 (3)	0.0096 (3)	−0.00147 (19)	0.00072 (18)	0.00172 (19)
As2	0.0100 (3)	0.0103 (3)	0.0074 (3)	−0.0014 (2)	0.00003 (18)	0.0014 (2)
As3	0.0066 (2)	0.0081 (3)	0.0074 (3)	0.00032 (19)	0.00102 (18)	0.00067 (19)
As4	0.0076 (2)	0.0075 (3)	0.0083 (3)	−0.00002 (19)	0.00122 (18)	−0.00046 (18)
O1	0.0154 (19)	0.0102 (19)	0.019 (2)	−0.0034 (16)	0.0032 (15)	−0.0008 (16)
O2	0.0134 (18)	0.017 (2)	0.0151 (19)	−0.0001 (16)	0.0077 (14)	−0.0027 (16)
O3	0.0036 (16)	0.016 (2)	0.025 (2)	−0.0003 (15)	0.0023 (14)	0.0049 (17)
O4	0.0077 (16)	0.0145 (19)	0.0136 (18)	0.0026 (15)	0.0024 (14)	0.0037 (15)
O5	0.0125 (18)	0.0120 (19)	0.025 (2)	−0.0018 (15)	−0.0103 (16)	−0.0004 (16)
O6	0.0127 (18)	0.017 (2)	0.0149 (19)	0.0003 (16)	0.0066 (14)	0.0055 (16)
O7	0.0139 (18)	0.0114 (19)	0.0103 (18)	0.0063 (15)	−0.0011 (14)	0.0018 (15)
O8	0.0169 (19)	0.0147 (19)	0.013 (2)	−0.0044 (16)	0.0005 (15)	−0.0055 (15)
O9	0.0089 (17)	0.0145 (19)	0.019 (2)	0.0014 (15)	0.0009 (15)	0.0017 (16)
O10	0.0145 (18)	0.0076 (18)	0.018 (2)	0.0010 (15)	0.0025 (15)	0.0047 (15)
O11	0.025 (2)	0.0084 (18)	0.0088 (18)	0.0017 (16)	0.0077 (15)	0.0018 (15)
O12	0.0063 (16)	0.024 (2)	0.018 (2)	−0.0019 (16)	−0.0012 (14)	0.0011 (17)
O13	0.035 (2)	0.0112 (19)	0.017 (2)	−0.0013 (18)	0.0032 (17)	−0.0012 (17)
O14	0.022 (2)	0.0135 (19)	0.013 (2)	−0.0012 (16)	−0.0021 (15)	0.0030 (16)
Na1	0.0255 (13)	0.0141 (12)	0.0370 (15)	−0.0030 (10)	0.0148 (11)	−0.0035 (11)

Geometric parameters (Å, º)

Al1—O12^i	1.906 (4)	Na2B—O3^ix	2.274 (10)
Al1—O12	1.906 (4)	Na2B—O3^iii	2.274 (10)
Al1—O1^ii	1.932 (4)	Na2B—O4^viii	2.477 (7)
Al1—O1^iii	1.932 (4)	Na2B—O2^viii	2.512 (9)
Al1—O3	1.994 (4)	Na2C—O13^ix	2.492 (9)
Al1—O3^i	1.994 (4)	Na2C—O3^iii	2.619 (9)
Al2—O14	1.920 (4)	Na2C—O2^viii	2.652 (10)
Al2—O10^iv	1.933 (4)	Na2C—O12^ix	2.931 (9)
Al2—O7^iv	1.942 (4)	Na2C—O10^iv	2.968 (11)
Al2—O5	1.947 (4)	Na3A—O2^iii	2.330 (6)
Al2—O9^v	1.955 (4)	Na3A—O8^v	2.353 (6)
Al2—O6^ii	2.000 (4)	Na3A—O6^ii	2.545 (7)
As1—O2	1.651 (4)	Na3A—O5^ii	2.879 (6)
As1—O1	1.676 (4)	Na3A—O13^ii	2.949 (7)
As1—O3	1.689 (4)	Na3B—O8^v	2.279 (8)
As1—O4	1.776 (4)	Na3B—O2^iii	2.451 (8)
As2—O13	1.638 (4)	Na3B—O13^ii	2.608 (9)
As2—O14	1.675 (4)	Na3B—O1^ii	2.725 (9)
As2—O12	1.686 (4)	Na3B—O4^ii	2.807 (8)
As2—O4	1.769 (4)	Na3B—O6^ii	2.980 (9)
As3—O7	1.668 (4)	Na4A—O2^i	2.213 (19)
As3—O5	1.671 (4)	Na4A—O8^v	2.271 (19)
As3—O6	1.677 (4)	Na4A—O13^ii	2.33 (2)
As3—O11	1.736 (4)	Na4A—O6^vii	2.79 (2)
As4—O8	1.646 (4)	Na4B—O14^x	2.449 (11)
As4—O10	1.676 (4)	Na4B—O8^v	2.512 (11)
As4—O9	1.679 (4)	Na4B—O10^v	2.555 (11)
As4—O11	1.760 (4)	Na4B—O2^i	2.568 (11)
Na1—O8^v	2.265 (5)	Na4B—O3^i	2.613 (11)
Na1—O9^vi	2.302 (5)	Na4B—O6^vii	2.854 (11)
Na1—O7^vii	2.429 (4)	Na4C—O8^v	2.278 (8)
Na1—O13^ii	2.492 (5)	Na4C—O2^i	2.310 (9)
Na1—O5^ii	2.517 (5)	Na4C—O13^ii	2.384 (9)
Na1—O9^ii	2.938 (5)	Na4C—O1^ii	2.538 (10)
Na1—O11^ii	2.966 (5)	Na4C—O3^i	2.954 (9)
Na1—O10^vi	3.013 (5)	Na4D—O8^v	2.28 (2)
Na2A—O2^viii	2.380 (11)	Na4D—O2^i	2.36 (2)
Na2A—O3^iii	2.420 (10)	Na4D—O6^vii	2.70 (2)
Na2A—O13^ix	2.631 (11)	Na4D—O14^x	2.78 (3)
Na2A—O3^ix	2.692 (12)	Na4D—O10^v	2.85 (2)
Na2A—O12^ix	2.962 (11)	Na4D—O3^i	2.89 (2)
O12^i—Al1—O12	179.7 (3)	O2—As1—O4	107.54 (19)
O12^i—Al1—O1^ii	94.10 (18)	O1—As1—O4	103.99 (19)
O12—Al1—O1^ii	86.13 (17)	O3—As1—O4	102.82 (18)
O12^i—Al1—O1^iii	86.13 (17)	O13—As2—O14	120.4 (2)
O12—Al1—O1^iii	94.10 (18)	O13—As2—O12	113.3 (2)
O1^ii—Al1—O1^iii	96.5 (3)	O14—As2—O12	107.8 (2)
O12^i—Al1—O3	89.56 (18)	O13—As2—O4	105.3 (2)
O12—Al1—O3	90.19 (17)	O14—As2—O4	100.13 (19)
O1^ii—Al1—O3	172.35 (19)	O12—As2—O4	108.58 (18)
O1^iii—Al1—O3	90.44 (16)	O7—As3—O5	114.24 (19)
O12^i—Al1—O3^i	90.19 (17)	O7—As3—O6	113.67 (19)
O12—Al1—O3^i	89.56 (18)	O5—As3—O6	109.9 (2)
O1^ii—Al1—O3^i	90.44 (16)	O7—As3—O11	109.49 (18)
O1^iii—Al1—O3^i	172.35 (19)	O5—As3—O11	105.4 (2)
O3—Al1—O3^i	82.8 (2)	O6—As3—O11	103.15 (19)
O14—Al2—O10^iv	89.86 (18)	O8—As4—O10	113.3 (2)
O14—Al2—O7^iv	174.86 (18)	O8—As4—O9	114.1 (2)
O10^iv—Al2—O7^iv	93.40 (17)	O10—As4—O9	111.99 (19)
O14—Al2—O5	88.99 (18)	O8—As4—O11	107.83 (19)
O10^iv—Al2—O5	86.32 (18)	O10—As4—O11	105.32 (18)
O7^iv—Al2—O5	95.18 (18)	O9—As4—O11	103.31 (19)
O14—Al2—O9^v	92.74 (18)	As1—O1—Al1^xi	137.9 (2)
O10^iv—Al2—O9^v	170.74 (18)	As1—O3—Al1	127.7 (2)
O7^iv—Al2—O9^v	84.66 (17)	As2—O4—As1	117.7 (2)
O5—Al2—O9^v	84.85 (18)	As3—O5—Al2	132.7 (2)
O14—Al2—O6^ii	83.26 (17)	As3—O6—Al2^xi	132.6 (2)
O10^iv—Al2—O6^ii	90.59 (17)	As3—O7—Al2^iv	130.6 (2)
O7^iv—Al2—O6^ii	92.73 (17)	As4—O9—Al2^v	138.8 (2)
O5—Al2—O6^ii	171.67 (19)	As4—O10—Al2^iv	129.4 (2)
O9^v—Al2—O6^ii	98.54 (17)	As3—O11—As4	127.6 (2)
O2—As1—O1	115.63 (19)	As2—O12—Al1	127.1 (2)
O2—As1—O3	112.7 (2)	As2—O14—Al2	130.2 (2)
O1—As1—O3	112.73 (19)

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