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Acta Crystallogr Sect E Struct Rep Online. 2008 June 1; 64(Pt 6): i36.
Published online 2008 May 21. doi:  10.1107/S1600536808014633
PMCID: PMC2961449

The alluaudite-like arsenate NaCaMg3(AsO4)3

Abstract

The title compound, sodium calcium trimagnesium tris­(arsenate), an alluaudite-like arsenate, was prepared by solid-state reaction at high temperature. The structure is built up from edge-sharing MgO6 octa­hedra in chains associated with the AsO4 arsenate groups. The three-dimensional network leads to two different tunnels occupied statistically by Na+ and Ca2+. One As and one Mg atom lie on twofold rotation axes; one Na and one Ca are disordered over two sites with occupancies of 0.7 and 0.3 and these sites lie on a twofold rotation axis and an inversion centre, respectively.

Related literature

For the alluaudite structure type, see: Moore (1971 [triangle]); Yakubovitch et al. (1977 [triangle]); Cu1.35Fe(PO4)3 (Warner et al., 1993 [triangle]); NaFe3.67(PO4)3 (Korzenski et al., 1998 [triangle]). For related alluaudite-like arsenates, see: NaCo3(AsO4)(HAsO4)2 (Kwang-Hwa & Pei-Fen, 1994 [triangle]); NaCaCdMg2(AsO4)3 (Khorari et al., 1997 [triangle]); Ag1.49Mn1.49Mn2(AsO4)3 (Ayed et al., 2002 [triangle]); Na1.72 Mn3.28(AsO4)3 (Brahim et al. 2003 [triangle]). For related literature, see: Leroux et al. (1995 [triangle]).

Experimental

Crystal data

  • NaCaMg3(AsO4)3
  • M r = 552.74
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-64-00i36-efi1.jpg
  • a = 11.880 (1) Å
  • b = 12.817 (1) Å
  • c = 6.741 (2) Å
  • β = 112.45 (1)°
  • V = 948.7 (3) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 11.36 mm−1
  • T = 293 (2) K
  • 0.6 × 0.2 × 0.15 mm

Data collection

  • Enraf–Nonius CAD-4 diffractometer
  • Absorption correction: ψ scan (North et al., 1968 [triangle]) T min = 0.110, T max = 0.180
  • 1358 measured reflections
  • 1154 independent reflections
  • 1133 reflections with I > 2σ(I)
  • R int = 0.021
  • 2 standard reflections frequency: 120 min intensity decay: 0.4%

Refinement

  • R[F 2 > 2σ(F 2)] = 0.022
  • wR(F 2) = 0.060
  • S = 1.29
  • 1154 reflections
  • 100 parameters
  • Δρmax = 0.99 e Å−3
  • Δρmin = −1.00 e Å−3

Data collection: CAD-4 EXPRESS (Duisenberg, 1992 [triangle]; Macíček & Yordanov, 1992 [triangle]); cell refinement: CAD-4 EXPRESS; data reduction: MolEN (Fair, 1990 [triangle]); program(s) used to solve structure: SHELXS86 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: DIAMOND (Brandenburg, 1998 [triangle]); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008 [triangle]).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808014633/br2069sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808014633/br2069Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Comment

The crystal structure of NaCaMg3(AsO4)3 is closely related to the common structure type of the well known mineral Alluaudite with the general formula X(1)X(2)M(1)M(2)2(PO4)3 (Moore, 1971; Yakubovitch et al., 1994). It can be described by a Mg3(AsO4)3 framework built up by a complex arrangement of distorted MgO6 octahedra, and AsO4 tetrahedra. The projection of the structure in a polyhedral representation is presented in Fig. 1. It consists of Mg1O6 and Mg2O6 octahedra that share edges to form staggered chains stacked parallel to the [10–1] direction. Equivalent chains are linked together through the AsO4 tetrahedra corners. As1O4 connects two chains and thus two of its O atoms belong of the same chain. The As2O4 tetrahedron shares his four oxygen summits with four different MgO6 octahedra belonging to three adjacent chains, two belong to the same chain and the two others from two different chains. The arrangement of magnesium octahedra Mg1O6 and Mg2O6 in chains present a distortion, with the mean Mg1—O and Mg2—O distances 2.135Å and 2.079Å respectively. The O—Mg1—O angles range from 73.28° to 112.20°, whereas the O—Mg2—O angles vary between 77.62° to 108.84°. The two crystallographic distinct As atoms are surrounded by four O atoms with the mean distance of As1—O: 1.691Å and As2—O: 1.694 Å. This structural arrangement delimits two types of hexagonal tunnels, parallel to the c axis and located at (1/2, 0, z) and (0,0,z) respectively. Sodium Na1, Na2 and calcium Ca1, Ca2 cations are located in those channels. The structure is closely related to the alluaudite structure type. In NaCaMg3(AsO4)3, the X(1) site at (1/2, 0, 0) is empty. Whereas the X(2) site at (0, 0, 0) contains 0.30 Na2 and 0.70 Ca2. The site in the tunnel at (0, 0, z) shifted from the X(2) site by ± 0.25 along z is occupied by Na1 and Ca1 with respectively the occupation number 0.70 and 0.30. There are a number of possible models for the cationic distribution and it's not possible to decide which is the best solution. We retain the solution with same amount of sodium and calcium. First, the occupancies of Na1 and Ca1 in the site shifted from X(2) were refined. Second, for the site X(2), the occupancies of Na2 and Ca2 were fixed to obtain the electroneutrality. For each two cations in the same site the atomic displacement parameters were maintained the same with the instruction EADP. The bond valence sum of the Na1, Na2, Ca2, Mg1, Mg2, As1 and As2 atoms are in a good agreement with their oxidation states (Brown & Altermatt, 1985). For the calcium Ca1 which occupy partialy the tunnel the bond valence sums is different (1.33).

Experimental

Single crystals of NaCaMg3(AsO4)3 were prepared by a mixture of NaNO3, CaCO3, MgN2O6(H2O)6 and NH4H2AsO4 with molar ratio of (1:1:2:3). The powder was ground, then heated in a porcelain crucible progressively until 1223 K. This temperature was held for 3 days. Then the mixture was cooled slowly to room temperature at 10 K/h. The product was washed with hot water. Prismatic and colorless crystals of the title compound were extracted. Their qualitative analysis by electron microscope probe revealed that it contains sodium, calcium, oxygen, arsenic and magnesium atoms.

Figures

Fig. 1.
Projection of the structure of NaCaMg3(AsO4)3 along [001] direction.
Fig. 2.
A view of a sheet showing the association mode of the MgO6 in chains with AsO4 tetrahedra shown with 50% probability displacement ellipsoids.

Crystal data

NaCaMg3(AsO4)3F000 = 1048
Mr = 552.74Dx = 3.870 Mg m3
Monoclinic, C2/cMo Kα radiation λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 25 reflections
a = 11.880 (1) Åθ = 2.4–28º
b = 12.817 (1) ŵ = 11.36 mm1
c = 6.741 (2) ÅT = 293 (2) K
β = 112.45 (1)ºPrismatic, colourless
V = 948.7 (3) Å30.6 × 0.2 × 0.15 mm
Z = 4

Data collection

Enraf–Nonius CAD-4 diffractometerRint = 0.021
Radiation source: fine-focus sealed tubeθmax = 28.0º
Monochromator: graphiteθmin = 2.4º
T = 293(2) Kh = −15→14
ω/2θ scansk = −1→16
Absorption correction: ψ scan(North et al., 1968)l = 0→8
Tmin = 0.110, Tmax = 0.1802 standard reflections
1358 measured reflections every 120 min
1154 independent reflections intensity decay: 0.4%
1133 reflections with I > 2σ(I)

Refinement

Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: full  w = 1/[σ2(Fo2) + (0.0244P)2 + 8.0874P] where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.022(Δ/σ)max < 0.001
wR(F2) = 0.060Δρmax = 0.99 e Å3
S = 1.29Δρmin = −1.00 e Å3
1154 reflectionsExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
100 parametersExtinction coefficient: 0.0071 (4)
Primary atom site location: structure-invariant direct methods

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 (Å2)

xyzUiso*/UeqOcc. (<1)
As10.26904 (3)0.38625 (2)0.37969 (5)0.00207 (13)
As20.50000.21057 (3)0.25000.00248 (14)
Mg10.50000.23783 (13)0.75000.0043 (3)
Mg20.78584 (10)0.15824 (9)0.37643 (18)0.0030 (2)
Na10.50000.511 (3)0.75000.019 (2)0.70
Ca10.50000.523 (3)0.75000.019 (2)0.30
Ca20.50000.00000.00000.0132 (3)0.70
Na20.50000.00000.00000.0132 (3)0.30
O10.4635 (2)0.28350 (19)0.0247 (4)0.0063 (5)
O20.2837 (2)0.31609 (19)0.1792 (4)0.0061 (5)
O30.3415 (2)0.32937 (19)0.6218 (4)0.0053 (5)
O40.1175 (2)0.39767 (19)0.3197 (4)0.0074 (5)
O50.6086 (2)0.1221 (2)0.2626 (4)0.0105 (5)
O60.3381 (2)0.50307 (19)0.3963 (4)0.0082 (5)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
As10.00076 (18)0.00152 (19)0.00403 (19)0.00028 (10)0.00101 (12)0.00027 (10)
As20.0017 (2)0.0013 (2)0.0040 (2)0.0000.00054 (16)0.000
Mg10.0020 (7)0.0036 (7)0.0080 (7)0.0000.0027 (6)0.000
Mg20.0021 (5)0.0022 (5)0.0053 (5)0.0000 (4)0.0022 (4)−0.0001 (4)
Na10.0091 (8)0.035 (7)0.0131 (8)0.0000.0032 (7)0.000
Ca10.0091 (8)0.035 (7)0.0131 (8)0.0000.0032 (7)0.000
Ca20.0161 (6)0.0036 (5)0.0107 (5)−0.0026 (4)−0.0051 (5)−0.0003 (4)
Na20.0161 (6)0.0036 (5)0.0107 (5)−0.0026 (4)−0.0051 (5)−0.0003 (4)
O10.0039 (11)0.0094 (11)0.0060 (11)0.0020 (9)0.0022 (9)0.0025 (9)
O20.0080 (11)0.0064 (11)0.0045 (11)0.0004 (9)0.0031 (9)−0.0010 (8)
O30.0050 (10)0.0072 (11)0.0033 (11)0.0043 (9)0.0010 (8)0.0022 (8)
O40.0006 (10)0.0065 (11)0.0142 (12)0.0005 (8)0.0016 (9)0.0000 (9)
O50.0034 (11)0.0071 (11)0.0169 (13)0.0038 (9)−0.0007 (9)−0.0040 (9)
O60.0089 (11)0.0022 (10)0.0138 (12)−0.0025 (9)0.0047 (10)−0.0007 (9)

Geometric parameters (Å, °)

As1—O21.687 (2)Na1—O1ix2.99 (3)
As1—O61.690 (2)Na1—O1viii2.99 (3)
As1—O31.692 (2)Ca1—O62.439 (5)
As1—O41.694 (2)Ca1—O6ii2.439 (5)
As2—O1i1.693 (2)Ca1—O6viii2.497 (6)
As2—O11.693 (2)Ca1—O6ix2.497 (6)
As2—O5i1.695 (2)Ca1—O1ix2.85 (4)
As2—O51.695 (2)Ca1—O1viii2.85 (4)
Mg1—O3ii2.104 (2)Ca1—O33.04 (4)
Mg1—O32.104 (2)Ca1—O3ii3.04 (4)
Mg1—O1iii2.139 (2)Ca2—O52.346 (3)
Mg1—O1i2.139 (2)Ca2—O5x2.346 (3)
Mg1—O4iv2.164 (3)Ca2—O4vii2.453 (3)
Mg1—O4v2.164 (3)Ca2—O4xi2.453 (3)
Mg2—O52.001 (3)Ca2—O4xii2.538 (3)
Mg2—O3vi2.068 (3)Ca2—O4vi2.538 (3)
Mg2—O6vii2.072 (3)Ca2—O5i2.872 (3)
Mg2—O2v2.077 (3)Ca2—O5xiii2.872 (3)
Mg2—O1v2.098 (3)Na2—O52.346 (3)
Mg2—O2i2.163 (3)Na2—O5x2.346 (3)
Na1—O62.428 (3)Na2—O4vii2.453 (3)
Na1—O6ii2.428 (3)Na2—O4xi2.453 (3)
Na1—O6viii2.481 (4)Na2—O4xii2.538 (3)
Na1—O6ix2.481 (4)Na2—O4vi2.538 (3)
Na1—O32.91 (3)Na2—O5i2.872 (3)
Na1—O3ii2.91 (3)Na2—O5xiii2.872 (3)
O2—As1—O6109.24 (12)O6—Ca1—O6ix92.2 (3)
O2—As1—O3111.91 (11)O6ii—Ca1—O6ix86.1 (2)
O6—As1—O3105.22 (12)O6—Ca1—O1ix121.1 (13)
O2—As1—O4106.26 (12)O6ii—Ca1—O1ix70.7 (6)
O6—As1—O4112.57 (12)O6viii—Ca1—O1ix83.7 (7)
O3—As1—O4111.73 (12)O6ix—Ca1—O1ix110.2 (10)
O1i—As2—O1112.96 (17)O6—Ca1—O1viii70.7 (6)
O1i—As2—O5i110.10 (13)O6ii—Ca1—O1viii121.1 (13)
O1—As2—O5i113.27 (12)O6viii—Ca1—O1viii110.2 (10)
O1i—As2—O5113.27 (12)O6ix—Ca1—O1viii83.7 (7)
O1—As2—O5110.10 (13)O6ii—Ca1—O3111.3 (13)
O5i—As2—O596.04 (18)O6viii—Ca1—O360.9 (6)
O3ii—Mg1—O3112.20 (15)O6ix—Ca1—O3105.3 (12)
O3ii—Mg1—O1iii86.41 (10)O6—Ca1—O3ii111.3 (13)
O3—Mg1—O1iii75.96 (9)O6viii—Ca1—O3ii105.3 (12)
O3ii—Mg1—O1i75.96 (9)O6ix—Ca1—O3ii60.9 (6)
O3—Mg1—O1i86.41 (10)O3—Ca1—O3ii70.2 (9)
O3—Mg1—O4iv87.51 (9)O5—Ca2—O4vii74.30 (9)
O1iii—Mg1—O4iv94.61 (10)O5x—Ca2—O4vii105.70 (9)
O1i—Mg1—O4iv111.02 (10)O5—Ca2—O4xi105.70 (9)
O3ii—Mg1—O4v87.51 (9)O5x—Ca2—O4xi74.30 (9)
O3—Mg1—O4v159.81 (11)O5—Ca2—O4xii103.17 (9)
O1iii—Mg1—O4v111.02 (10)O5x—Ca2—O4xii76.83 (9)
O1i—Mg1—O4v94.61 (10)O4vii—Ca2—O4xii62.31 (10)
O4iv—Mg1—O4v73.28 (14)O4xi—Ca2—O4xii117.69 (10)
O5—Mg2—O3vi108.84 (12)O5—Ca2—O4vi76.83 (9)
O5—Mg2—O6vii92.76 (11)O5x—Ca2—O4vi103.17 (9)
O3vi—Mg2—O6vii86.82 (11)O4vii—Ca2—O4vi117.69 (10)
O5—Mg2—O2v90.41 (11)O4xi—Ca2—O4vi62.31 (10)
O6vii—Mg2—O2v101.79 (11)O5—Ca2—O5i56.66 (10)
O3vi—Mg2—O1v77.62 (10)O4vii—Ca2—O5i91.59 (8)
O6vii—Mg2—O1v95.10 (11)O4xi—Ca2—O5i88.41 (8)
O2v—Mg2—O1v82.14 (10)O4xii—Ca2—O5i64.46 (7)
O5—Mg2—O2i82.74 (10)O4vi—Ca2—O5i115.54 (7)
O3vi—Mg2—O2i90.36 (10)O5x—Ca2—O5xiii56.66 (10)
O2v—Mg2—O2i82.81 (10)O4vii—Ca2—O5xiii88.41 (8)
O1v—Mg2—O2i89.86 (10)O4xi—Ca2—O5xiii91.59 (8)
O6—Na1—O6viii86.76 (12)O4xii—Ca2—O5xiii115.54 (7)
O6ii—Na1—O6viii92.89 (13)O4vi—Ca2—O5xiii64.46 (7)
O6—Na1—O6ix92.89 (13)O5—Na2—O4vii74.30 (9)
O6ii—Na1—O6ix86.76 (12)O5x—Na2—O4vii105.70 (9)
O6—Na1—O359.6 (5)O5—Na2—O4xi105.70 (9)
O6ii—Na1—O3116.0 (11)O5x—Na2—O4xi74.30 (9)
O6viii—Na1—O363.1 (5)O5—Na2—O4xii103.17 (9)
O6ix—Na1—O3109.6 (10)O5x—Na2—O4xii76.83 (9)
O6—Na1—O3ii116.0 (11)O4vii—Na2—O4xii62.31 (10)
O6viii—Na1—O3ii109.6 (10)O4xi—Na2—O4xii117.69 (10)
O6ix—Na1—O3ii63.1 (5)O5—Na2—O4vi76.83 (9)
O3—Na1—O3ii73.7 (8)O5x—Na2—O4vi103.17 (9)
O6—Na1—O1ix116.3 (11)O4vii—Na2—O4vi117.69 (10)
O6ii—Na1—O1ix68.4 (5)O4xi—Na2—O4vi62.31 (10)
O6viii—Na1—O1ix81.2 (6)O4vii—Na2—O5i91.59 (8)
O6ix—Na1—O1ix106.4 (9)O4xi—Na2—O5i88.41 (8)
O6—Na1—O1viii68.4 (5)O4xii—Na2—O5i64.46 (7)
O6ii—Na1—O1viii116.3 (11)O4vi—Na2—O5i115.54 (7)
O6viii—Na1—O1viii106.4 (9)O4vii—Na2—O5xiii88.41 (8)
O6ix—Na1—O1viii81.2 (6)O4xi—Na2—O5xiii91.59 (8)
O6—Ca1—O6viii86.1 (2)O4xii—Na2—O5xiii115.54 (7)
O6ii—Ca1—O6viii92.2 (3)O4vi—Na2—O5xiii64.46 (7)

Symmetry codes: (i) −x+1, y, −z+1/2; (ii) −x+1, y, −z+3/2; (iii) x, y, z+1; (iv) −x+1/2, −y+1/2, −z+1; (v) x+1/2, −y+1/2, z+1/2; (vi) x+1/2, −y+1/2, z−1/2; (vii) x+1/2, y−1/2, z; (viii) x, −y+1, z+1/2; (ix) −x+1, −y+1, −z+1; (x) −x+1, −y, −z; (xi) −x+1/2, −y+1/2, −z; (xii) −x+1/2, y−1/2, −z+1/2; (xiii) x, −y, z−1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BR2069).

References

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