inorganic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2056-9890

The aluminoarsenate K1.8Sr0.6Al3(AsO4)4

aInstitut Supérieur des Sciences Appliquées et Technologie de Gabès, Avenue Omar Ibn El Khattab, 6072 Zrig, Gabès, Tunisia, and bLaboratoire de Matériaux et Cristallochime, Institut Supérieur des Sciences Appliquées et Technologie de Mahdia, Avenue El Mourouj, Sidi Messoud 5111 Hiboun, Mahdia, Tunisia
*Correspondence e-mail: haj_anissa@yahoo.fr

(Received 20 March 2012; accepted 2 April 2012; online 13 April 2012)

The title compound, potassium strontium trialuminium tetra­arsenate, was prepared by solid-state reaction. The structure consists of AlO6 octa­hedra (site symmetries 2.. and 2/m) and two AsO4 tetra­hedra (.2. and m..) sharing corners and edges to form a two-dimensional structure parallel to (010). The cations are occupationally disordered and are located in the interlayer space. For both types of cations, distorted coordination polyhedra are observed.

Related literature

For further information on this structure type, see: K3Cr3(AsO4)4 (Friaa et al., 2003[Friaa, B. B., Boughzalza, H. & Jouini, T. (2003). J. Solid State Chem. 173, 273-279.]); K3Fe3(AsO4)4 (Ouerfelli et al., 2005[Ouerfelli, N., Zid, M. F. & Jouini, T. (2005). Acta Cryst. E61, i67-i69.]). For similar structures, see: K3Fe3(PO4)4·H2O (Lii, 1995[Lii, K.-H. (1995). Eur. J. Solid State Inorg. Chem. 32, 917-926.]); Na3Fe3(PO4)4 (Lajmi et al., 2002[Lajmi, B., Hidouri, M., Rzaigui, M. & Ben Amara, M. (2002). Mat. Res. Bull. 37, 2407-2416.]). For background to the bond-valence method, see: Brown & Altermatt (1985[Brown, I. D. & Altermatt, D. (1985). Acta Cryst. B41, 244-247.]).

Experimental

Crystal data
  • K1.8Sr0.6Al3(AsO4)4

  • Mr = 759.57

  • Orthorhombic, C m c e

  • a = 10.567 (3) Å

  • b = 20.531 (4) Å

  • c = 6.388 (1) Å

  • V = 1385.9 (5) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 12.67 mm−1

  • T = 293 K

  • 0.36 × 0.22 × 0.14 mm

Data collection
  • Enraf–Nonius CAD-4 diffractometer

  • Absorption correction: ψ scan (North et al., 1968[North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351-359.]) Tmin = 0.088, Tmax = 0.292

  • 1510 measured reflections

  • 796 independent reflections

  • 704 reflections with I > 2σ(I)

  • Rint = 0.024

  • 2 standard reflections every 120 min intensity decay: 0.4%

Refinement
  • R[F2 > 2σ(F2)] = 0.039

  • wR(F2) = 0.112

  • S = 1.09

  • 796 reflections

  • 88 parameters

  • Δρmax = 1.68 e Å−3

  • Δρmin = −1.45 e Å−3

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994[Enraf-Nonius (1994). CAD-4 EXPRESS. Enraf-Nonius, Delft, The Netherlands.]); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995[Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany.]); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: DIAMOND (Brandenburg, 1998[Brandenburg, K. (1998). DIAMOND. Crystal Impact GbR, Bonn, Germany.]); software used to prepare material for publication: WinGX (Farrugia, 1999[Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837-838.]).

Supporting information


Comment top

The crystal structure of K1.8Sr0.6Al3(AsO4)4 is a two-dimensional network formed by curved layers perpendicular to the b axis. Each layer consists of AlO6 octahedra and AsO4 tetrahedra sharing corners and edges (Fig. 1). This structural arrangement leads to six-membered windows within the layer (Fig. 2). It is isostructural with the compounds K3Cr3(AsO4)4 (Friaa et al., 2003) and K3Fe3(AsO4)4 (Ouerfelli et al., 2005). The asymmetric unit is the link-up of two AlO6 octahedra and As2O4 tetrahedron by corners and As1O4 tetrahedron by edges (Fig. 3). The common edge O4···O4, is the shortest oxygen distance. The As1O4 tetrahedron lies on two fold axis and is distorted. It has two type of As—O bonds, two short distances and two long distances involving the bridging oxygen atoms O4. The As2O4 tetrahedron is located on mirror plane. It shares two oxygen atoms O5 with two equivalent Al1O6 octahedra and one oxygen atom O1, which is situated on mirror plane, with Al2O6 octahedron. The fourth oxygen atom O2 which lies on mirror plane is not coordinated and points to the interlayer space. The Al1O6 octahedron is strongly distorted which the O4—Al1—O4 angle 75.6 ° is more acute than those according to an ideal octahedron. The mean distance of Al1—O 1.930 (4) Å. The Al2O6 octahedron which lies on a crystallographic center of symmetry is less distorted than the Al1O6 octahedron which lies on a two fold axis. The structure is characterized by two cationic sites. The site (0, 1/2, 1/2) located in the interlayer space and the site (1/4, 1/2, 1/4) confined in windows. The difference to be indicated is the cationic distribution in the similar structure compounds. Both strontium cations Sr1 and Sr2 occupy the windows and the potassium cations K1 and K2 are located in interlayers space of the structure. The bond valence sum of the K1, K2 and Sr1 are in a good agreement with their oxidation states (Brown & Altermatt, 1985). But for the Sr2, the bond strength is higher than the expected value +2 suggesting that the SrO9 appear too small for this ion which is acceptable given the small number of Sr atoms that occupy this site. The valence sums around the Al atoms are both low (2.6 vu) but attempts to introduce other elements onto these sites were not successfull. The resulting difference electron density contains several large features reflecting the difficulty in determining the precise locations of Sr and and K.

Related literature top

For further information on this structure type, see: K3Cr3(AsO4)4 (Friaa et al., 2003); K3Fe3(AsO4)4 (Ouerfelli et al., 2005). For similar bidimensional networks, see: K3Fe3(PO4)4.H2O (Lii, 1995); Na3Fe3(PO4)4 (Lajmi et al., 2002). For background to the bond-valence method, see: Brown & Altermatt (1985).

Experimental top

The purpose is to obtain a phase from the molars proportions of (2:0.5:4) of a mixture of KNO3, Sr(NO3)2 and NH4H2AsO4. The mixture was finely ground and calcined at 723 K in a porcelain crucible. Then the temperature was held at 943 K during 26 h. A slow cooling in a speed of 2 K/h until 893 K and of 5 K/h until 823 K was proceeded. The fusion was reached. A long wash in the boiling water allowed us to isolate some parallelepipedic colourless crystals with acceptable size for an analysis by X-ray diffraction on single-crystal. The qualitative analysis by electron microscope probe of a selected crystal revealed the presence of aluminium atom which comes from the crucible, as well as the different elements of the compound composition.

Refinement top

The localization of the strontium and potassium atoms is delicate because of the existence of disorder. The Fourier difference synthesis reveals an intense peak and three nearby peaks relatively less intense. It was then necessary to take considering the peaks which could have a structural meaning because of their environments in atoms of oxygen. A constraint, respecting the electroneutrality, was applied to the occupation rates of the cations. Furthermore, the refinement anisotropy leading to very deformed ellipsoids, the condition EADP allowed by the program SHELX was applied. The high value of the electron densities occurs at 1.68 e/A3 from heavy atom As1 is due to the effects of Fourier series termination.

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, 1998); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. : Projection of the structure of K1.8Sr0.6Al3(AsO4)4 along the c axis.
[Figure 2] Fig. 2. : A view of a layer showing the windows.
[Figure 3] Fig. 3. : The asymmetric unit of the structure of K1.8Sr0.6Al3(AsO4)4.
potassium strontium trialuminium tetraarsenate top
Crystal data top
K1.8Sr0.6Al3(AsO4)4F(000) = 1424
Mr = 759.57Dx = 3.641 Mg m3
Orthorhombic, CmceMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2bc 2Cell parameters from 25 reflections
a = 10.567 (3) Åθ = 2.2–27°
b = 20.531 (4) ŵ = 12.67 mm1
c = 6.388 (1) ÅT = 293 K
V = 1385.9 (5) Å3Parallelipedic, colourless
Z = 40.36 × 0.22 × 0.14 mm
Data collection top
Enraf–Nonius CAD-4
diffractometer
704 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.024
Graphite monochromatorθmax = 27.0°, θmin = 3.8°
ω/2θ scansh = 130
Absorption correction: ψ scan
(North et al., 1968)
k = 260
Tmin = 0.088, Tmax = 0.292l = 88
1510 measured reflections2 standard reflections every 120 min
796 independent reflections intensity decay: 0.4%
Refinement top
Refinement on F2Primary atom site location: real-space vector search
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.039 w = 1/[σ2(Fo2) + (0.0826P)2]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.112(Δ/σ)max < 0.001
S = 1.09Δρmax = 1.68 e Å3
796 reflectionsΔρmin = 1.45 e Å3
88 parametersExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.0006 (3)
Crystal data top
K1.8Sr0.6Al3(AsO4)4V = 1385.9 (5) Å3
Mr = 759.57Z = 4
Orthorhombic, CmceMo Kα radiation
a = 10.567 (3) ŵ = 12.67 mm1
b = 20.531 (4) ÅT = 293 K
c = 6.388 (1) Å0.36 × 0.22 × 0.14 mm
Data collection top
Enraf–Nonius CAD-4
diffractometer
704 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.024
Tmin = 0.088, Tmax = 0.2922 standard reflections every 120 min
1510 measured reflections intensity decay: 0.4%
796 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.03988 parameters
wR(F2) = 0.1120 restraints
S = 1.09Δρmax = 1.68 e Å3
796 reflectionsΔρmin = 1.45 e Å3
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)
As10.75000.54444 (4)0.25000.0058 (3)
As20.00000.65488 (4)0.05958 (11)0.0070 (3)
Al10.75000.40809 (11)0.25000.0054 (5)
Al20.00000.50000.00000.0069 (6)
Sr10.010 (3)0.6619 (4)0.4463 (8)0.056 (4)0.12 (2)
Sr20.006 (8)0.5644 (17)0.477 (4)0.056 (4)0.03 (2)
K10.2111 (8)0.7265 (4)0.3993 (12)0.062 (2)0.33 (1)
K20.258 (2)0.7305 (10)0.190 (3)0.062 (2)0.12 (1)
O10.00000.5866 (3)0.0858 (7)0.0090 (10)
O20.00000.7176 (3)0.1009 (9)0.0180 (12)
O30.7104 (3)0.59095 (18)0.0477 (5)0.0092 (7)
O40.6367 (3)0.48557 (16)0.2962 (5)0.0078 (7)
O50.1259 (3)0.65351 (18)0.2222 (5)0.0120 (8)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
As10.0061 (4)0.0055 (4)0.0057 (4)0.0000.0008 (2)0.000
As20.0047 (4)0.0081 (4)0.0083 (4)0.0000.0000.0014 (2)
Al10.0042 (10)0.0075 (11)0.0046 (9)0.0000.0008 (6)0.000
Al20.0026 (13)0.0090 (15)0.0088 (13)0.0000.0000.0000 (11)
Sr10.058 (7)0.074 (5)0.034 (2)0.038 (9)0.004 (5)0.003 (2)
Sr20.058 (7)0.074 (5)0.034 (2)0.038 (9)0.004 (5)0.003 (2)
K10.074 (5)0.051 (3)0.060 (5)0.037 (4)0.002 (4)0.011 (3)
K20.074 (5)0.051 (3)0.060 (5)0.037 (4)0.002 (4)0.011 (3)
O10.008 (2)0.008 (2)0.010 (2)0.0000.0000.0038 (19)
O20.022 (3)0.014 (3)0.018 (3)0.0000.0000.004 (2)
O30.0094 (17)0.0098 (18)0.0084 (15)0.0029 (15)0.0011 (13)0.0003 (13)
O40.0086 (16)0.0060 (16)0.0088 (15)0.0033 (15)0.0017 (14)0.0011 (11)
O50.0089 (18)0.0115 (17)0.0155 (18)0.0023 (16)0.0024 (14)0.0051 (13)
Geometric parameters (Å, º) top
As1—O3i1.661 (3)Sr1—O22.489 (8)
As1—O31.661 (3)Sr1—O5xiii2.565 (17)
As1—O4i1.727 (3)Sr1—O3ix2.57 (2)
As1—O41.727 (3)Sr1—O2xiv2.666 (10)
As2—O21.646 (6)Sr1—O3xi2.75 (3)
As2—O11.682 (5)Sr1—O12.775 (9)
As2—O5ii1.688 (3)Sr2—O3ix2.23 (9)
As2—O51.688 (3)Sr2—O4xv2.67 (4)
Al1—O5iii1.831 (4)Sr2—O4ix2.75 (4)
Al1—O5iv1.831 (4)Sr2—O12.54 (2)
Al1—O3v1.947 (3)Sr2—O5xii2.94 (5)
Al1—O3vi1.947 (3)Sr2—O3xi2.36 (8)
Al1—O4i2.013 (4)K1—O5xiv2.735 (7)
Al1—O42.013 (4)K1—O3ix2.804 (8)
Al2—O1vii1.861 (5)K1—O2xiv2.819 (8)
Al2—O11.861 (5)K1—O22.940 (9)
Al2—O4viii1.967 (3)K2—O5xvi2.69 (2)
Al2—O4ix1.967 (3)K2—O22.80 (3)
Al2—O4x1.967 (3)K2—O5xiv2.817 (19)
Al2—O4xi1.967 (3)K2—O2xvii2.90 (2)
Sr1—O5xii2.450 (15)K2—O3xviii3.02 (2)
O3i—As1—O3109.8 (2)O5xiii—Sr1—O3ix114.3 (3)
O3i—As1—O4i111.16 (17)O5xii—Sr1—O2xiv76.4 (3)
O3—As1—O4i116.37 (16)O2—Sr1—O2xiv84.2 (2)
O3i—As1—O4116.37 (16)O5xiii—Sr1—O2xiv74.6 (3)
O3—As1—O4111.16 (17)O3ix—Sr1—O2xiv123.7 (9)
O4i—As1—O491.2 (2)O5xii—Sr1—O3xi112.0 (5)
O2—As2—O1108.0 (3)O2—Sr1—O3xi102.6 (7)
O2—As2—O5ii113.34 (17)O5xiii—Sr1—O3xi58.5 (5)
O1—As2—O5ii109.03 (16)O3ix—Sr1—O3xi113.5 (3)
O2—As2—O5113.34 (17)O2xiv—Sr1—O3xi116.9 (8)
O1—As2—O5109.03 (16)O5xii—Sr1—O1134.2 (6)
O5ii—As2—O5104.0 (2)O2—Sr1—O161.2 (2)
O5iii—Al1—O5iv92.6 (2)O5xiii—Sr1—O1128.7 (9)
O5iii—Al1—O3v93.80 (16)O3ix—Sr1—O174.3 (3)
O5iv—Al1—O3v87.00 (16)O2xiv—Sr1—O1145.3 (3)
O5iii—Al1—O3vi87.00 (16)O3xi—Sr1—O171.6 (4)
O5iv—Al1—O3vi93.80 (16)O3ix—Sr2—O4xv69 (2)
O3v—Al1—O3vi178.8 (3)O3ix—Sr2—O4ix67.4 (18)
O5iii—Al1—O4i96.06 (14)O4xv—Sr2—O4ix90.0 (17)
O5iv—Al1—O4i170.55 (17)O3ix—Sr2—O185.0 (19)
O3v—Al1—O4i88.66 (15)O4xv—Sr2—O1147 (3)
O3vi—Al1—O4i90.43 (15)O4ix—Sr2—O159.7 (7)
O5iii—Al1—O4170.55 (17)O4xv—Sr2—O5xii61.2 (11)
O5iv—Al1—O496.06 (14)O4ix—Sr2—O5xii125 (3)
O3v—Al1—O490.43 (15)O1—Sr2—O5xii123 (2)
O3vi—Al1—O488.66 (15)O3ix—Sr2—O3xi151.3 (17)
O4i—Al1—O475.6 (2)O4xv—Sr2—O3xi130 (2)
O1vii—Al2—O1180.0 (3)O4ix—Sr2—O3xi125 (2)
O1vii—Al2—O4viii87.08 (14)O1—Sr2—O3xi82.4 (17)
O1—Al2—O4viii92.92 (14)O5xii—Sr2—O3xi108.5 (13)
O1vii—Al2—O4ix92.92 (14)O5xiv—K1—O3ix158.0 (4)
O1—Al2—O4ix87.08 (14)O5xiv—K1—O2xiv60.2 (2)
O4viii—Al2—O4ix85.5 (2)O3ix—K1—O2xiv110.3 (3)
O1vii—Al2—O4x87.08 (14)O5xiv—K1—O267.8 (2)
O1—Al2—O4x92.92 (14)O3ix—K1—O290.8 (3)
O4viii—Al2—O4x94.5 (2)O2xiv—K1—O273.8 (2)
O4ix—Al2—O4x180.0O5xvi—K2—O2123.0 (7)
O1vii—Al2—O4xi92.92 (14)O5xvi—K2—O5xiv57.4 (4)
O1—Al2—O4xi87.08 (14)O2—K2—O5xiv68.8 (5)
O4viii—Al2—O4xi180.00 (19)O5xvi—K2—O2xvii69.0 (6)
O4ix—Al2—O4xi94.5 (2)O2—K2—O2xvii160.9 (8)
O4x—Al2—O4xi85.5 (2)O5xiv—K2—O2xvii114.9 (8)
O5xii—Sr1—O2145.1 (10)O5xvi—K2—O3xviii144.3 (9)
O5xii—Sr1—O5xiii64.0 (2)O2—K2—O3xviii87.6 (7)
O2—Sr1—O5xiii137.6 (9)O5xiv—K2—O3xviii156.4 (10)
O5xii—Sr1—O3ix62.4 (5)O2xvii—K2—O3xviii87.4 (5)
O2—Sr1—O3ix108.1 (7)
Symmetry codes: (i) x+3/2, y, z+1/2; (ii) x, y, z; (iii) x+1, y+1, z; (iv) x+1/2, y+1, z+1/2; (v) x, y+1, z; (vi) x+3/2, y+1, z+1/2; (vii) x, y+1, z; (viii) x1/2, y+1, z1/2; (ix) x1/2, y, z+1/2; (x) x+1/2, y+1, z1/2; (xi) x+1/2, y, z+1/2; (xii) x, y, z+1; (xiii) x, y, z+1; (xiv) x, y+3/2, z+1/2; (xv) x1/2, y+1, z+1/2; (xvi) x+1/2, y+3/2, z; (xvii) x+1/2, y, z+1/2; (xviii) x+1, y, z.

Experimental details

Crystal data
Chemical formulaK1.8Sr0.6Al3(AsO4)4
Mr759.57
Crystal system, space groupOrthorhombic, Cmce
Temperature (K)293
a, b, c (Å)10.567 (3), 20.531 (4), 6.388 (1)
V3)1385.9 (5)
Z4
Radiation typeMo Kα
µ (mm1)12.67
Crystal size (mm)0.36 × 0.22 × 0.14
Data collection
DiffractometerEnraf–Nonius CAD-4
diffractometer
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.088, 0.292
No. of measured, independent and
observed [I > 2σ(I)] reflections
1510, 796, 704
Rint0.024
(sin θ/λ)max1)0.638
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.039, 0.112, 1.09
No. of reflections796
No. of parameters88
Δρmax, Δρmin (e Å3)1.68, 1.45

Computer programs: CAD-4 EXPRESS (Enraf–Nonius, 1994), XCAD4 (Harms & Wocadlo, 1995), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 1998), WinGX (Farrugia, 1999).

 

References

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