supplementary materials


Acta Cryst. (2014). E70, i6    [ doi:10.1107/S1600536813033850 ]

The aluminoarsenate Na1.67K1.33Al3(AsO4)4

M. A. Bouhassine and H. Boughzala

Abstract top

The title compound, sodium potassium trialuminium tetra­kis­(orthoarsenate), was prepared by solid-state reactions. The anionic framework consists of corrugated layers parallel to (010) and is made up of corner-sharing AlO6 octa­hedra (site symmetries .2. and 2/m..) that are connected to isolated AsO4 tetra­hedra (site symmetries .2. and m..) through edge- and corner-sharing. The alkali cations are occupationally disordered. The two K+ cations [site symmetries .2. and m..; occupancies 0.314 (7) and 0.035 (12)] are situated in the inter­layer space, whereas the smaller Na+ cations [both with site symmetry m..; occupancies = 0.725 (14) and 0.112 (14)] are located in the cavities of the anionic framework. The K+ cations are surrounded by six and seven O atoms, the Na+ cations by seven and nine O atoms. The resulting coordination polyhedra of the two types of cations are highly distorted.

Comment top

Na1.67K1.33Al3(AsO4)4 is isostructural with K3Cr3(AsO4)4 (Friaa et al. (2003)) and belongs to the AIMIII(XO4)4 family of compounds (AI = alkali metal, MIII = Al, Cr, Fe,.. X = As, P) . Its structure consists of AlO6 octahedra and AsO4 tetrahedra sharing corners and edges to form a two-dimensional framework (Fig.1) that consists of corrugated layers extending parallel to (010). Each layer lies on a c-glide plane perpendicular to the b axis at y = 0 and y = 1/2. In the asymmetric unit two AlO6 octahedra are linked to an As1O4 tetrahedron by sharing corners and to an As2O4 tetrahedron by sharing edges. The alkali cations are occupationally disordered with occupancies of 0.725 (14), 0.112 (14), 0.314 (7) and 0.035 (12) for Na1, Na2, K1 and K2, leading to the chemical formula Na1.67K1.33Al3(AsO4)4. Smaller than K+, the seven- and nine-coordinated Na1+ and Na2+ (rNa+ = 1.02 Å), are located in cavities surrounded by the anionic framework (Fig. 2). On the other hand, the K1+ and K2+ cations (rK+ = 1.38 Å) are surrounded, respectively, by seven and six O atoms and are located in larger sites in the corrugated interlayer space. Using the bond valence method (Brown, 2002), the calculated bond-valence sum values (in valence units) of 5.17, 4.98, 3.04, 3.03, 0.86, 1.11, 0.92, 0.86, respectively, for As1, As2, Al1, Al2, Na1, Na2, K1 and K2 are in good agreement with the expected oxidation states.

A similar distribution of cations was observed in K1.8Sr0.6Al3(AsO4)4 (Haj Abdallah et al., 2012). In fact, smaller than K+, the Sr2+ cations (rSr2+ = 1.18 Å) are located in the anionic cavities, on the other hand, K+ occupy the interlayer space. The cationic distribution in these two structures make it reasonable to conclude that the interlayer space is reserved for bigger cations and the anionic cavities for smaller cations. To our knowledge, this is the first published structure with occupationally disordered alkali sites in the AIMIII(XO4)4 family of compounds. Reports of some new members of this family will be published soon.

Related literature top

For further information on this structure type, see: Friaa et al. (2003); Haj Abdallah & Haddad (2012). For background to the bond-valence method, see: Brown (2002).

Experimental top

Crystals of Na1.67K1.33Al3(AsO4)4 were obtained from a mixture of K2CO3, Al2O3 and NH4H2AsO4 in the stoichiometric molar ratio K/Al/As=2/3/4. The mixture was finely ground and heated in a porcelain crucible at 723 K for 4 h to eliminate volatile products. The temperature was held at 1173 K during 10 days until fusion was reached. The sample was slowly cooled in a speed of 5 K/ h to 923 K and finally quenched to room temperature. A long wash with boiling water liberated colorless crystals. The qualitative analysis by electron microscope probe of a selected crystal revealed the presence of the different elements in the compound composition. It is most likely that the incorporated sodium stems from the crucible.

Refinement top

Except for K2 and Na2, both with a very low occupation, all atoms were refined with anisotropic displacement parameters. Constraints were applied to the Na+ and K+ cation occupation rates to achieve electro-neutrality. The highest and lowest values of the electron densities occurare located 0.97 Å and 0.80 Å, respectively, from As2.

Computing details top

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS (Enraf–Nonius, 1994); 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, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. Projection of the Na1.67K1.33Al3(AsO4)4 structure along [100], showing the K1+ and K2+ cations in the corrugated interlayer space. Displacement ellipsoids are drawn at the 90% probability level.
[Figure 2] Fig. 2. Cavities limited by the anionic framework hosting Na+ cations in the Na1.67K1.33Al3(AsO4)4 structure.
Sodium potassium trialuminium tetrakis(orthoarsenate) top
Crystal data top
Na1.67K1.33Al3(AsO4)4F(000) = 1370.4
Mr = 726.95Dx = 3.563 Mg m3
Orthorhombic, CmceMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2bc 2Cell parameters from 25 reflections
a = 10.493 (1) Åθ = 3.8–27°
b = 20.395 (4) ŵ = 10.53 mm1
c = 6.335 (4) ÅT = 293 K
V = 1355.7 (9) Å3Plate, colourless
Z = 40.40 × 0.10 × 0.07 mm
Data collection top
Enraf–Nonius CAD-4
diffractometer
717 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.062
Graphite monochromatorθmax = 27.0°, θmin = 3.8°
ω/2θ scansh = 131
Absorption correction: ψ scan
(North et al., 1968)
k = 261
Tmin = 0.130, Tmax = 0.332l = 88
1723 measured reflections2 standard reflections every 120 min
780 independent reflections intensity decay: 1.1%
Refinement top
Refinement on F21 restraint
Least-squares matrix: fullPrimary atom site location: structure-invariant direct methods
R[F2 > 2σ(F2)] = 0.038Secondary atom site location: difference Fourier map
wR(F2) = 0.112 w = 1/[σ2(Fo2) + (0.0727P)2 + 0.5867P]
where P = (Fo2 + 2Fc2)/3
S = 1.15(Δ/σ)max < 0.001
780 reflectionsΔρmax = 2.38 e Å3
84 parametersΔρmin = 1.33 e Å3
Crystal data top
Na1.67K1.33Al3(AsO4)4V = 1355.7 (9) Å3
Mr = 726.95Z = 4
Orthorhombic, CmceMo Kα radiation
a = 10.493 (1) ŵ = 10.53 mm1
b = 20.395 (4) ÅT = 293 K
c = 6.335 (4) Å0.40 × 0.10 × 0.07 mm
Data collection top
Enraf–Nonius CAD-4
diffractometer
717 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.062
Tmin = 0.130, Tmax = 0.332θmax = 27.0°
1723 measured reflections2 standard reflections every 120 min
780 independent reflections intensity decay: 1.1%
Refinement top
R[F2 > 2σ(F2)] = 0.038Δρmax = 2.38 e Å3
wR(F2) = 0.112Δρmin = 1.33 e Å3
S = 1.15Absolute structure: ?
780 reflectionsAbsolute structure parameter: ?
84 parametersRogers parameter: ?
1 restraint
Special details top

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 (Å2) top
xyzUiso*/UeqOcc. (<1)
As10.00000.15486 (3)0.05909 (10)0.0075 (3)
As20.25000.04448 (3)0.25000.0070 (3)
Al10.00000.00000.00000.0063 (5)
Al20.25000.09187 (10)0.25000.0073 (4)
O10.00000.2179 (3)0.1020 (8)0.0163 (10)
O20.1263 (3)0.15363 (15)0.2215 (5)0.0110 (7)
O30.00000.0854 (2)0.0873 (7)0.0095 (9)
O40.2105 (3)0.09062 (16)0.4534 (4)0.0102 (6)
O50.1364 (3)0.01511 (13)0.2027 (5)0.0086 (6)
Na10.00000.1628 (3)0.5513 (7)0.0350 (18)0.725 (14)
Na20.00000.0635 (17)0.520 (5)0.042 (12)*0.112 (14)
K10.2125 (6)0.2737 (3)0.1075 (10)0.048 (2)0.314 (7)
K20.25000.271 (3)0.25000.03 (2)*0.035 (12)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
As10.0016 (4)0.0103 (4)0.0108 (4)0.0000.0000.0013 (2)
As20.0039 (4)0.0086 (4)0.0084 (4)0.0000.0005 (2)0.000
Al10.0011 (10)0.0090 (12)0.0089 (11)0.0000.0000.0003 (10)
Al20.0028 (9)0.0093 (9)0.0099 (9)0.0000.0001 (6)0.000
O10.020 (3)0.013 (2)0.016 (2)0.0000.0000.006 (2)
O20.0045 (15)0.0124 (15)0.0161 (15)0.0010 (11)0.0040 (13)0.0019 (11)
O30.006 (2)0.009 (2)0.0133 (19)0.0000.0000.0024 (17)
O40.0091 (15)0.0116 (15)0.0100 (13)0.0029 (12)0.0009 (12)0.0017 (11)
O50.0033 (14)0.0105 (15)0.0120 (13)0.0023 (11)0.0018 (13)0.0007 (10)
Na10.037 (3)0.047 (3)0.020 (3)0.0000.0000.0033 (19)
K10.053 (3)0.034 (3)0.059 (4)0.029 (3)0.013 (3)0.003 (2)
Geometric parameters (Å, º) top
As1—O11.642 (5)O4—Na2xv2.284 (9)
As1—O2i1.678 (3)O4—Na1xv2.655 (4)
As1—O21.678 (3)O4—K1xvi2.795 (6)
As1—O31.694 (4)O4—K2xvi3.13 (5)
As2—O4ii1.648 (3)O5—Na22.66 (3)
As2—O41.648 (3)O5—Na2xv2.77 (3)
As2—O51.729 (3)Na1—Na22.03 (4)
As2—O5ii1.729 (3)Na1—O1xvii2.467 (7)
As2—Al22.781 (2)Na1—O2i2.481 (5)
Al1—O31.827 (5)Na1—K1viii2.603 (8)
Al1—O3iii1.827 (5)Na1—K1xviii2.603 (8)
Al1—O5iii1.947 (3)Na1—O1xviii2.619 (8)
Al1—O5iv1.947 (3)Na1—O4xv2.655 (4)
Al1—O5i1.947 (3)Na1—O4vi2.655 (4)
Al1—O51.947 (3)Na1—O3xvii2.781 (7)
Al2—O2ii1.817 (3)Na1—K2xix3.21 (2)
Al2—O21.817 (3)Na2—O4vi2.284 (9)
Al2—O4v1.924 (3)Na2—O4xv2.284 (9)
Al2—O4vi1.924 (3)Na2—O3xvii2.53 (3)
Al2—O5ii1.991 (3)Na2—Na2xv2.60 (7)
Al2—O51.991 (3)Na2—O5i2.66 (3)
Al2—Na23.19 (2)Na2—O5vi2.77 (3)
Al2—Na2vii3.19 (2)Na2—O5xv2.77 (3)
Al2—Na1vii3.552 (3)Na2—O2i2.95 (3)
Al2—Na13.552 (3)Na2—As2xiv3.025 (17)
Al2—K1viii3.579 (6)K1—K20.986 (7)
O1—Na1ix2.467 (7)K1—K1xi1.846 (12)
O1—Na1x2.620 (8)K1—K1ii1.969 (14)
O1—K2x2.795 (5)K1—K2xi2.47 (2)
O1—K2xi2.795 (5)K1—Na1x2.603 (8)
O1—K1i2.833 (7)K1—O4xx2.795 (6)
O1—K12.833 (7)K1—O1xviii2.896 (6)
O1—K1x2.896 (6)K1—O2xii2.999 (7)
O1—K1xii2.896 (6)K1—O1xi3.022 (6)
O1—K1xi3.022 (6)K1—O2xi3.067 (6)
O1—K1xiii3.022 (6)K2—K1ii0.986 (7)
O2—Na12.481 (5)K2—K1viii2.47 (2)
O2—K12.708 (6)K2—K1xi2.47 (2)
O2—K22.73 (5)K2—O2ii2.73 (5)
O2—Na22.95 (3)K2—O1xi2.795 (5)
O2—K1viii2.999 (7)K2—O1xviii2.795 (5)
O2—K1xi3.067 (6)K2—O4xx3.13 (5)
O2—K1ii3.166 (7)K2—O4xxi3.13 (5)
O3—Na2ix2.53 (3)K2—Na1x3.21 (2)
O3—Na1ix2.781 (7)K2—Na1xix3.21 (2)
O4—Al2xiv1.924 (3)
O1—As1—O2i113.13 (15)O4xv—Na2—O2109.3 (12)
O1—As1—O2113.13 (15)O3xvii—Na2—O2121.4 (11)
O2i—As1—O2104.3 (2)Na2xv—Na2—O2123.8 (17)
O1—As1—O3108.4 (3)O5i—Na2—O289.3 (10)
O2i—As1—O3108.86 (14)O5—Na2—O260.3 (6)
O2—As1—O3108.86 (14)O5vi—Na2—O2122.25 (12)
O4ii—As2—O4110.4 (2)O5xv—Na2—O2175.4 (8)
O4ii—As2—O5116.04 (14)O2i—Na2—O253.4 (6)
O4—As2—O5111.32 (15)Na1—Na2—As2xiv94.7 (8)
O4ii—As2—O5ii111.32 (15)O4vi—Na2—As2xiv32.5 (3)
O4—As2—O5ii116.04 (14)O4xv—Na2—As2xiv146.6 (14)
O5—As2—O5ii90.65 (19)O3xvii—Na2—As2xiv63.2 (6)
O4ii—As2—Al2124.81 (11)Na2xv—Na2—As2xiv85.4 (10)
O4—As2—Al2124.81 (11)O5i—Na2—As2xiv141.6 (11)
O5—As2—Al245.33 (10)O5—Na2—As2xiv81.4 (3)
O5ii—As2—Al245.33 (10)O5vi—Na2—As2xiv34.3 (3)
O3—Al1—O3iii180.0O5xv—Na2—As2xiv93.9 (10)
O3—Al1—O5iii87.19 (13)O2i—Na2—As2xiv141.0 (10)
O3iii—Al1—O5iii92.81 (13)O2—Na2—As2xiv89.9 (4)
O3—Al1—O5iv87.19 (13)O2—K1—O4xx158.4 (3)
O3iii—Al1—O5iv92.81 (13)K2—K1—O1136 (2)
O5iii—Al1—O5iv94.60 (18)K1xi—K1—O177.3 (4)
O3—Al1—O5i92.80 (13)K1ii—K1—O1138.1 (3)
O3iii—Al1—O5i87.20 (13)K2xi—K1—O163.1 (4)
O5iii—Al1—O5i85.40 (18)Na1x—K1—O157.43 (19)
O5iv—Al1—O5i180.0O2—K1—O159.97 (16)
O3—Al1—O592.80 (13)O4xx—K1—O1109.1 (3)
O3iii—Al1—O587.19 (13)K2—K1—O1xviii74.3 (4)
O5iii—Al1—O5180.0K1xi—K1—O1xviii145.9 (4)
O5iv—Al1—O585.40 (18)K1ii—K1—O1xviii74.1 (3)
O5i—Al1—O594.60 (18)K2xi—K1—O1xviii136.6 (5)
O2ii—Al2—O292.3 (2)Na1x—K1—O1xviii53.00 (18)
O2ii—Al2—O4v87.27 (15)O2—K1—O1xviii68.10 (17)
O2—Al2—O4v93.78 (15)O4xx—K1—O1xviii91.3 (2)
O2ii—Al2—O4vi93.78 (15)O1—K1—O1xviii73.48 (15)
O2—Al2—O4vi87.27 (15)K2—K1—O2xii153 (3)
O4v—Al2—O4vi178.5 (2)K1xi—K1—O2xii77.6 (4)
O2ii—Al2—O5ii95.88 (12)K1ii—K1—O2xii150.20 (12)
O2—Al2—O5ii171.00 (15)K2xi—K1—O2xii59.0 (10)
O4v—Al2—O5ii90.44 (14)Na1x—K1—O2xii51.99 (17)
O4vi—Al2—O5ii88.37 (14)O2—K1—O2xii124.3 (2)
O2ii—Al2—O5171.00 (15)O4xx—K1—O2xii52.81 (14)
O2—Al2—O595.89 (12)O1—K1—O2xii65.11 (18)
O4v—Al2—O588.37 (14)O1xviii—K1—O2xii104.9 (3)
O4vi—Al2—O590.44 (14)K2—K1—O1xi67.3 (4)
O5ii—Al2—O576.27 (18)K1xi—K1—O1xi66.1 (4)
O2ii—Al2—As2133.87 (11)K1ii—K1—O1xi67.1 (3)
O2—Al2—As2133.87 (11)K2xi—K1—O1xi81.5 (2)
O4v—Al2—As289.24 (12)Na1x—K1—O1xi145.6 (2)
O4vi—Al2—As289.24 (12)O2—K1—O1xi112.8 (3)
O5ii—Al2—As238.14 (9)O4xx—K1—O1xi87.10 (17)
O5—Al2—As238.14 (9)O1—K1—O1xi143.4 (2)
As1—O2—Al2129.43 (18)O1xviii—K1—O1xi140.6 (2)
As1—O3—Al1129.2 (3)O2xii—K1—O1xi105.27 (19)
As2—O4—Al2xiv135.8 (2)K2—K1—O2xi115.2 (17)
As2—O5—Al1120.66 (15)K1xi—K1—O2xi61.0 (3)
As2—O5—Al296.54 (14)K1ii—K1—O2xi113.7 (4)
Al1—O5—Al2131.59 (15)K2xi—K1—O2xi57.9 (10)
O2—Na1—O3xvii130.6 (2)Na1x—K1—O2xi98.0 (2)
K1viii—Na1—O3xvii99.79 (19)O2—K1—O2xi143.4 (2)
K1xviii—Na1—O3xvii99.79 (19)O4xx—K1—O2xi55.33 (12)
O1xviii—Na1—O3xvii146.4 (2)O1—K1—O2xi108.0 (2)
O4xv—Na1—O3xvii72.21 (14)O1xviii—K1—O2xi145.9 (3)
O4vi—Na1—O3xvii72.21 (14)O2xii—K1—O2xi51.17 (15)
Na2—Na1—As181.5 (10)O1xi—K1—O2xi54.13 (14)
O1xvii—Na1—As1155.8 (3)K1ii—K2—K1174 (6)
O2i—Na1—As132.36 (9)K1ii—K2—K1viii40.9 (15)
O2—Na1—As132.36 (9)K1—K2—K1viii142 (2)
K1viii—Na1—As199.35 (18)K1ii—K2—K1xi142 (2)
K1xviii—Na1—As199.35 (18)K1—K2—K1xi40.9 (15)
O1xviii—Na1—As171.20 (16)K1viii—K2—K1xi137 (2)
O4xv—Na1—As187.71 (12)K1ii—K2—O2107 (3)
O4vi—Na1—As187.71 (12)K1—K2—O278 (3)
O3xvii—Na1—As1142.4 (2)K1viii—K2—O270.1 (11)
Na2—Na1—K2xix117.1 (10)K1xi—K2—O272.0 (11)
O1xvii—Na1—K2xix57.3 (3)K1ii—K2—O2ii78 (3)
O2i—Na1—K2xix143.1 (5)K1—K2—O2ii107 (3)
O2—Na1—K2xix85.70 (14)K1viii—K2—O2ii72.0 (11)
K1viii—Na1—K2xix15.5 (4)K1xi—K2—O2ii70.1 (11)
K1xviii—Na1—K2xix116.0 (8)O2—K2—O2ii57.3 (11)
O1xviii—Na1—K2xix75.8 (9)K1ii—K2—O1xi85.9 (5)
O4xv—Na1—K2xix156.7 (5)K1—K2—O1xi93.7 (5)
O4vi—Na1—K2xix63.7 (8)K1viii—K2—O1xi119.1 (6)
O3xvii—Na1—K2xix85.1 (6)K1xi—K2—O1xi64.7 (2)
As1—Na1—K2xix114.45 (17)O2—K2—O1xi119.6 (16)
Na1—Na2—O4vi75.6 (9)O2ii—K2—O1xi69.3 (6)
Na1—Na2—O4xv75.6 (9)K1ii—K2—O1xviii93.7 (5)
O4vi—Na2—O4xv150.7 (17)K1—K2—O1xviii85.9 (5)
Na1—Na2—O3xvii74.3 (11)K1viii—K2—O1xviii64.7 (2)
O4vi—Na2—O3xvii83.4 (9)K1xi—K2—O1xviii119.1 (6)
O4xv—Na2—O3xvii83.4 (9)O2—K2—O1xviii69.3 (6)
Na1—Na2—Na2xv180 (2)O2ii—K2—O1xviii119.6 (16)
O4vi—Na2—Na2xv104.4 (9)O1xi—K2—O1xviii171 (2)
O4xv—Na2—Na2xv104.4 (9)K1ii—K2—O4xx113 (4)
O3xvii—Na2—Na2xv105.8 (19)K1—K2—O4xx62 (3)
Na1—Na2—O5i116.3 (13)K1viii—K2—O4xx133.6 (15)
O4vi—Na2—O5i131.8 (13)K1xi—K2—O4xx88.7 (8)
O4xv—Na2—O5i67.9 (5)O2—K2—O4xx134.51 (15)
O3xvii—Na2—O5i144.1 (7)O2ii—K2—O4xx151.78 (16)
Na2xv—Na2—O5i63.6 (11)O1xi—K2—O4xx85.1 (10)
Na1—Na2—O5116.3 (13)O1xviii—K2—O4xx86.7 (10)
O4vi—Na2—O567.9 (5)K1ii—K2—O4xxi62 (3)
O4xv—Na2—O5131.8 (13)K1—K2—O4xxi113 (4)
O3xvii—Na2—O5144.1 (7)K1viii—K2—O4xxi88.7 (8)
Na2xv—Na2—O563.6 (11)K1xi—K2—O4xxi133.6 (15)
O5i—Na2—O565.1 (8)O2—K2—O4xxi151.78 (16)
Na1—Na2—O5vi120.9 (12)O2ii—K2—O4xxi134.51 (15)
O4vi—Na2—O5vi66.1 (5)O1xi—K2—O4xxi86.7 (10)
O4xv—Na2—O5vi126.3 (13)O1xviii—K2—O4xxi85.1 (10)
O3xvii—Na2—O5vi58.6 (7)O4xx—K2—O4xxi51.3 (9)
Na2xv—Na2—O5vi59.2 (11)K1ii—K2—Na1x132 (2)
O5i—Na2—O5vi122.8 (13)K1—K2—Na1x45.0 (15)
O5—Na2—O5vi89.2 (7)K1viii—K2—Na1x112.6 (2)
Na1—Na2—O5xv120.9 (12)K1xi—K2—Na1x85.8 (3)
O4vi—Na2—O5xv126.3 (13)O2—K2—Na1x87.4 (4)
O4xv—Na2—O5xv66.1 (5)O2ii—K2—Na1x141.5 (14)
O3xvii—Na2—O5xv58.6 (7)O1xi—K2—Na1x127.1 (11)
Na2xv—Na2—O5xv59.2 (11)O1xviii—K2—Na1x48.0 (3)
O5i—Na2—O5xv89.2 (7)O4xx—K2—Na1x49.6 (6)
O5—Na2—O5xv122.8 (13)O4xxi—K2—Na1x83.8 (12)
O5vi—Na2—O5xv62.1 (8)K1ii—K2—Na1xix45.0 (15)
Na1—Na2—O2i56.1 (8)K1—K2—Na1xix132 (2)
O4vi—Na2—O2i109.3 (12)K1viii—K2—Na1xix85.8 (3)
O4xv—Na2—O2i57.4 (6)K1xi—K2—Na1xix112.6 (2)
O3xvii—Na2—O2i121.4 (11)O2—K2—Na1xix141.5 (14)
Na2xv—Na2—O2i123.8 (17)O2ii—K2—Na1xix87.4 (4)
O5i—Na2—O2i60.3 (6)O1xi—K2—Na1xix48.0 (3)
O5—Na2—O2i89.3 (10)O1xviii—K2—Na1xix127.1 (11)
O5vi—Na2—O2i175.4 (8)O4xx—K2—Na1xix83.8 (12)
O5xv—Na2—O2i122.25 (12)O4xxi—K2—Na1xix49.6 (6)
Na1—Na2—O256.1 (8)Na1x—K2—Na1xix130.3 (18)
O4vi—Na2—O257.4 (6)
Symmetry codes: (i) x, y, z; (ii) x+1/2, y, z+1/2; (iii) x, y, z; (iv) x, y, z; (v) x+1/2, y, z1/2; (vi) x, y, z+1; (vii) x+1/2, y, z+1/2; (viii) x, y+1/2, z+1/2; (ix) x, y, z1; (x) x, y+1/2, z1/2; (xi) x+1/2, y+1/2, z; (xii) x, y+1/2, z1/2; (xiii) x1/2, y+1/2, z; (xiv) x+1/2, y, z+1/2; (xv) x, y, z+1; (xvi) x, y1/2, z+1/2; (xvii) x, y, z+1; (xviii) x, y+1/2, z+1/2; (xix) x+1/2, y+1/2, z+1; (xx) x, y+1/2, z+1/2; (xxi) x+1/2, y+1/2, z.
Selected bond lengths (Å) top
As1—O11.642 (5)Al1—O5iii1.947 (3)
As1—O2i1.678 (3)Al1—O5iv1.947 (3)
As1—O21.678 (3)Al1—O5i1.947 (3)
As1—O31.694 (4)Al1—O51.947 (3)
As2—O4ii1.648 (3)Al2—O2ii1.817 (3)
As2—O41.648 (3)Al2—O21.817 (3)
As2—O51.729 (3)Al2—O4v1.924 (3)
As2—O5ii1.729 (3)Al2—O4vi1.924 (3)
Al1—O31.827 (5)Al2—O5ii1.991 (3)
Al1—O3iii1.827 (5)Al2—O51.991 (3)
Symmetry codes: (i) x, y, z; (ii) x+1/2, y, z+1/2; (iii) x, y, z; (iv) x, y, z; (v) x+1/2, y, z1/2; (vi) x, y, z+1.
Acknowledgements top

No acknowledgement

references
References top

Brandenburg, K. (2006). DIAMOND. Crystal Impact GbR, Bonn, Germany.

Brown, I. D. (2002). In The Chemical Bond in Inorganic Chemistry: The Bond Valence Model. Oxford University Press.

Enraf–Nonius (1994). CAD-4 EXPRESS. Enraf–Nonius, Delft, The Nether- lands.

Friaa, B. B., Boughzala, H. & Jouini, T. (2003). J. Solid State Chem. 173, 273–279.

Haj Abdallah, A. & Haddad, A. (2012). Acta Cryst. E68, i29.

Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany.

North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351–359.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.

Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925.