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Hydro­thermally prepared mansfieldite, AlAsO4·2H2O (aluminium arsenate dihydrate), contains a vertex-sharing three-dimensional network of cis-AlO4(H2O)2 octahedra and AsO4 tetrahedra [dav(Al-O) = 1.907 (2) Å, dav(As-O) = 1.685 (2) Å and [theta]av(Al-O-As) = 134.5 (1)°].

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100011690/qa0377sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270100011690/qa0377Isup2.hkl
Contains datablock I

Comment top

On the basis of cell parameters, symmetry and composition, the present phase is a synthetic analogue of mansfieldite, AlAsO4·2H2O (Allen et al., 1948; Ronis & D'Yvoire, 1969). Mansfieldite is a member of the MIIIXO4·2H2O (M = Al, Fe, Ga, Cr; X = P, As) family of phases exemplified by variscite, AlPO4·2H2O (Kniep et al., 1977).

The cis-AlO4(H2O)2 octahedron [dav(Al—O) = 1.907 (2) Å] and AsO4 tetrahedron [dav(As—O) = 1.685 (2) Å] share vertices, as Al—O—As bonds [O1—O4 with θav = 134.5 (1)°], resulting in a three-dimensional network of polyhedra. Three of the four water H atoms participate in O—H···O hydrogen bonds in a similar manner to that seen in variscite (Kniep et al., 1977).

Experimental top

A starting mixture of KOH (1 M, 4 ml), Al(NO3)3 (0.5 M, 8 ml) and H3AsO4 (1 M, 4 ml) was heated to 443 K in a 23-ml-capacity teflon-lined hydrothermal bomb for 4 d. Upon cooling the bomb to ambient temperature over a period of 2–3 h, a crop of small (to 0.1 mm) blocks and octahedra of the title compound was recovered by vacuum filtration and washing with water and acetone.

Computing details top

Data collection: SMART (Bruker, 1999); cell refinement: SMART; data reduction: SMART; program(s) used to refine structure: CRYSTALS (Watkin et al., 1997); software used to prepare material for publication: CRYSTALS.

(I) top
Crystal data top
Al·AsO4·2(H2O)Dx = 3.06 Mg m3
Mr = 201.93Melting point: not measured K
Orthorhombic, PbcaMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2abCell parameters from 2390 reflections
a = 8.8218 (5) Åθ = 3.7–30.7°
b = 9.8252 (6) ŵ = 7.89 mm1
c = 10.1163 (6) ÅT = 298 K
V = 876.8 (2) Å3Faceted block, colourless
Z = 80.08 × 0.08 × 0.08 mm
F(000) = 784
Data collection top
Bruker SMART1000 CCD area-detector
diffractometer
1587 independent reflections
Radiation source: fine-focus sealed tube1059 reflections with I > σ(I)
Graphite monochromatorRint = 0.039
ω scansθmax = 32.5°, θmin = 1.0°
Absorption correction: multi-scan
(SADABS; Bruker, 1999)
h = 129
Tmin = 0.470, Tmax = 0.532k = 1411
8491 measured reflectionsl = 1411
Refinement top
Refinement on FSecondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.025All H-atom parameters refined
wR(F2) = 0.026 Chebychev polynomial with 3 parameters (Carruthers & Watkin, 1979): 0.139, 0.174, 0.091
S = 1.05(Δ/σ)max = 0.000112
1059 reflectionsΔρmax = 0.73 e Å3
90 parametersΔρmin = 0.68 e Å3
Primary atom site location: structure-invariant direct methods
Crystal data top
Al·AsO4·2(H2O)V = 876.8 (2) Å3
Mr = 201.93Z = 8
Orthorhombic, PbcaMo Kα radiation
a = 8.8218 (5) ŵ = 7.89 mm1
b = 9.8252 (6) ÅT = 298 K
c = 10.1163 (6) Å0.08 × 0.08 × 0.08 mm
Data collection top
Bruker SMART1000 CCD area-detector
diffractometer
1587 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 1999)
1059 reflections with I > σ(I)
Tmin = 0.470, Tmax = 0.532Rint = 0.039
8491 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.02590 parameters
wR(F2) = 0.026All H-atom parameters refined
S = 1.05Δρmax = 0.73 e Å3
1059 reflectionsΔρmin = 0.68 e Å3
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Al10.14889 (11)0.1802 (1)0.12793 (9)0.0076
As10.03564 (3)0.13830 (3)0.15010 (3)0.0060
O10.0117 (2)0.0316 (2)0.1429 (2)0.0093
O20.0029 (3)0.2008 (2)0.3008 (2)0.0102
O30.2175 (3)0.1700 (2)0.1096 (2)0.0106
O40.0835 (3)0.2172 (2)0.0438 (2)0.0112
O50.2283 (3)0.1234 (3)0.2958 (2)0.0112
O60.3175 (3)0.0703 (3)0.0562 (3)0.0139
H510.19 (1)0.170 (8)0.354 (7)0.08 (3)*
H520.309 (7)0.114 (6)0.301 (6)0.036 (17)*
H610.347 (7)0.093 (6)0.010 (6)0.033 (16)*
H620.295 (8)0.023 (7)0.053 (7)0.047 (18)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Al10.0088 (4)0.0066 (4)0.0074 (4)0.0003 (3)0.0005 (3)0.0005 (3)
As10.00708 (12)0.00490 (12)0.00611 (12)0.00004 (12)0.00034 (13)0.00017 (12)
O10.010 (1)0.0046 (8)0.014 (1)0.0002 (7)0.0002 (9)0.0014 (8)
O20.0132 (12)0.010 (1)0.0076 (9)0.0019 (8)0.0005 (8)0.0031 (8)
O30.007 (1)0.0071 (9)0.017 (1)0.0017 (8)0.0020 (9)0.0017 (8)
O40.012 (1)0.0138 (11)0.008 (1)0.0061 (9)0.0045 (9)0.0003 (9)
O50.0102 (11)0.0149 (11)0.0085 (9)0.004 (1)0.0014 (8)0.0007 (9)
O60.0161 (12)0.0100 (11)0.0155 (13)0.0003 (9)0.003 (1)0.000 (1)
Geometric parameters (Å, º) top
Al1—O11.903 (2)As1—O21.679 (2)
Al1—O2i1.883 (3)As1—O31.685 (2)
Al1—O3ii1.894 (2)As1—O41.692 (2)
Al1—O4iii1.866 (3)O5—H510.81 (8)
Al1—O51.920 (3)O5—H520.72 (7)
Al1—O61.977 (3)O6—H610.76 (6)
As1—O11.684 (2)O6—H620.94 (7)
O1—Al1—O2i90.62 (11)O1—As1—O3106.99 (11)
O1—Al1—O3ii178.59 (12)O2—As1—O3110.24 (12)
O2i—Al1—O3ii88.91 (11)O1—As1—O4110.42 (12)
O1—Al1—O4iii91.56 (11)O2—As1—O4106.51 (12)
O2i—Al1—O4iii91.38 (12)O3—As1—O4110.62 (12)
O3ii—Al1—O4iii87.12 (11)Al1—O1—As1133.20 (13)
O1—Al1—O586.46 (11)Al1iv—O2—As1135.50 (15)
O2i—Al1—O595.27 (11)Al1v—O3—As1135.42 (14)
O3ii—Al1—O594.91 (12)Al1iii—O4—As1133.99 (14)
O4iii—Al1—O5173.07 (12)Al1—O5—H51110 (6)
O1—Al1—O695.07 (11)Al1—O5—H52117 (5)
O2i—Al1—O6174.14 (12)H51—O5—H52113 (8)
O3ii—Al1—O685.43 (11)Al1—O6—H61115 (5)
O4iii—Al1—O689.85 (12)Al1—O6—H62113 (4)
O5—Al1—O683.73 (12)H61—O6—H62110 (6)
O1—As1—O2112.10 (12)
Symmetry codes: (i) x, y+1/2, z+1/2; (ii) x+1/2, y+1/2, z; (iii) x, y, z; (iv) x, y1/2, z+1/2; (v) x+1/2, y1/2, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O5—H51···O4i0.82 (8)1.78 (8)2.592 (3)169 (8)
O5—H52···O1vi0.72 (6)2.04 (6)2.729 (3)160 (6)
O6—H62···O30.94 (7)1.70 (7)2.578 (4)155 (7)
Symmetry codes: (i) x, y+1/2, z+1/2; (vi) x+1/2, y, z+1/2.

Experimental details

Crystal data
Chemical formulaAl·AsO4·2(H2O)
Mr201.93
Crystal system, space groupOrthorhombic, Pbca
Temperature (K)298
a, b, c (Å)8.8218 (5), 9.8252 (6), 10.1163 (6)
V3)876.8 (2)
Z8
Radiation typeMo Kα
µ (mm1)7.89
Crystal size (mm)0.08 × 0.08 × 0.08
Data collection
DiffractometerBruker SMART1000 CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 1999)
Tmin, Tmax0.470, 0.532
No. of measured, independent and
observed [I > σ(I)] reflections
8491, 1587, 1059
Rint0.039
(sin θ/λ)max1)0.756
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.025, 0.026, 1.05
No. of reflections1059
No. of parameters90
No. of restraints?
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.73, 0.68

Computer programs: SMART (Bruker, 1999), SMART, CRYSTALS (Watkin et al., 1997), CRYSTALS.

Selected geometric parameters (Å, º) top
Al1—O11.903 (2)Al1—O61.977 (3)
Al1—O2i1.883 (3)As1—O11.684 (2)
Al1—O3ii1.894 (2)As1—O21.679 (2)
Al1—O4iii1.866 (3)As1—O31.685 (2)
Al1—O51.920 (3)As1—O41.692 (2)
Al1—O1—As1133.20 (13)Al1v—O3—As1135.42 (14)
Al1iv—O2—As1135.50 (15)Al1iii—O4—As1133.99 (14)
Symmetry codes: (i) x, y+1/2, z+1/2; (ii) x+1/2, y+1/2, z; (iii) x, y, z; (iv) x, y1/2, z+1/2; (v) x+1/2, y1/2, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O5—H51···O4i0.82 (8)1.78 (8)2.592 (3)169 (8)
O5—H52···O1vi0.72 (6)2.04 (6)2.729 (3)160 (6)
O6—H62···O30.94 (7)1.70 (7)2.578 (4)155 (7)
Symmetry codes: (i) x, y+1/2, z+1/2; (vi) x+1/2, y, z+1/2.
 

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