Hydrothermally prepared mansfieldite, AlAsO
4·2H
2O (aluminium arsenate dihydrate), contains a vertex-sharing three-dimensional network of
cis-AlO
4(H
2O)
2 octahedra and AsO
4 tetrahedra [
dav(Al-O) = 1.907 (2) Å,
dav(As-O) = 1.685 (2) Å and
av(Al-O-As) = 134.5 (1)°].
Supporting information
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.
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.
Crystal data top
Al·AsO4·2(H2O) | Dx = 3.06 Mg m−3 |
Mr = 201.93 | Melting point: not measured K |
Orthorhombic, Pbca | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ac 2ab | Cell parameters from 2390 reflections |
a = 8.8218 (5) Å | θ = 3.7–30.7° |
b = 9.8252 (6) Å | µ = 7.89 mm−1 |
c = 10.1163 (6) Å | T = 298 K |
V = 876.8 (2) Å3 | Faceted block, colourless |
Z = 8 | 0.08 × 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 tube | 1059 reflections with I > σ(I) |
Graphite monochromator | Rint = 0.039 |
ω scans | θmax = 32.5°, θmin = 1.0° |
Absorption correction: multi-scan (SADABS; Bruker, 1999) | h = −12→9 |
Tmin = 0.470, Tmax = 0.532 | k = −14→11 |
8491 measured reflections | l = −14→11 |
Refinement top
Refinement on F | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.025 | All 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 reflections | Δρmax = 0.73 e Å−3 |
90 parameters | Δρmin = −0.68 e Å−3 |
Primary atom site location: structure-invariant direct methods | |
Crystal data top
Al·AsO4·2(H2O) | V = 876.8 (2) Å3 |
Mr = 201.93 | Z = 8 |
Orthorhombic, Pbca | Mo Kα radiation |
a = 8.8218 (5) Å | µ = 7.89 mm−1 |
b = 9.8252 (6) Å | T = 298 K |
c = 10.1163 (6) Å | 0.08 × 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 = 0.532 | Rint = 0.039 |
8491 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.025 | 90 parameters |
wR(F2) = 0.026 | All H-atom parameters refined |
S = 1.05 | Δρmax = 0.73 e Å−3 |
1059 reflections | Δρmin = −0.68 e Å−3 |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Al1 | 0.14889 (11) | 0.1802 (1) | 0.12793 (9) | 0.0076 | |
As1 | 0.03564 (3) | −0.13830 (3) | 0.15010 (3) | 0.0060 | |
O1 | 0.0117 (2) | 0.0316 (2) | 0.1429 (2) | 0.0093 | |
O2 | −0.0029 (3) | −0.2008 (2) | 0.3008 (2) | 0.0102 | |
O3 | 0.2175 (3) | −0.1700 (2) | 0.1096 (2) | 0.0106 | |
O4 | −0.0835 (3) | −0.2172 (2) | 0.0438 (2) | 0.0112 | |
O5 | 0.2283 (3) | 0.1234 (3) | 0.2958 (2) | 0.0112 | |
O6 | 0.3175 (3) | 0.0703 (3) | 0.0562 (3) | 0.0139 | |
H51 | 0.19 (1) | 0.170 (8) | 0.354 (7) | 0.08 (3)* | |
H52 | 0.309 (7) | 0.114 (6) | 0.301 (6) | 0.036 (17)* | |
H61 | 0.347 (7) | 0.093 (6) | −0.010 (6) | 0.033 (16)* | |
H62 | 0.295 (8) | −0.023 (7) | 0.053 (7) | 0.047 (18)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Al1 | 0.0088 (4) | 0.0066 (4) | 0.0074 (4) | −0.0003 (3) | 0.0005 (3) | 0.0005 (3) |
As1 | 0.00708 (12) | 0.00490 (12) | 0.00611 (12) | 0.00004 (12) | 0.00034 (13) | 0.00017 (12) |
O1 | 0.010 (1) | 0.0046 (8) | 0.014 (1) | −0.0002 (7) | −0.0002 (9) | −0.0014 (8) |
O2 | 0.0132 (12) | 0.010 (1) | 0.0076 (9) | −0.0019 (8) | 0.0005 (8) | 0.0031 (8) |
O3 | 0.007 (1) | 0.0071 (9) | 0.017 (1) | 0.0017 (8) | 0.0020 (9) | 0.0017 (8) |
O4 | 0.012 (1) | 0.0138 (11) | 0.008 (1) | −0.0061 (9) | −0.0045 (9) | 0.0003 (9) |
O5 | 0.0102 (11) | 0.0149 (11) | 0.0085 (9) | 0.004 (1) | −0.0014 (8) | −0.0007 (9) |
O6 | 0.0161 (12) | 0.0100 (11) | 0.0155 (13) | 0.0003 (9) | 0.003 (1) | −0.000 (1) |
Geometric parameters (Å, º) top
Al1—O1 | 1.903 (2) | As1—O2 | 1.679 (2) |
Al1—O2i | 1.883 (3) | As1—O3 | 1.685 (2) |
Al1—O3ii | 1.894 (2) | As1—O4 | 1.692 (2) |
Al1—O4iii | 1.866 (3) | O5—H51 | 0.81 (8) |
Al1—O5 | 1.920 (3) | O5—H52 | 0.72 (7) |
Al1—O6 | 1.977 (3) | O6—H61 | 0.76 (6) |
As1—O1 | 1.684 (2) | O6—H62 | 0.94 (7) |
| | | |
O1—Al1—O2i | 90.62 (11) | O1—As1—O3 | 106.99 (11) |
O1—Al1—O3ii | 178.59 (12) | O2—As1—O3 | 110.24 (12) |
O2i—Al1—O3ii | 88.91 (11) | O1—As1—O4 | 110.42 (12) |
O1—Al1—O4iii | 91.56 (11) | O2—As1—O4 | 106.51 (12) |
O2i—Al1—O4iii | 91.38 (12) | O3—As1—O4 | 110.62 (12) |
O3ii—Al1—O4iii | 87.12 (11) | Al1—O1—As1 | 133.20 (13) |
O1—Al1—O5 | 86.46 (11) | Al1iv—O2—As1 | 135.50 (15) |
O2i—Al1—O5 | 95.27 (11) | Al1v—O3—As1 | 135.42 (14) |
O3ii—Al1—O5 | 94.91 (12) | Al1iii—O4—As1 | 133.99 (14) |
O4iii—Al1—O5 | 173.07 (12) | Al1—O5—H51 | 110 (6) |
O1—Al1—O6 | 95.07 (11) | Al1—O5—H52 | 117 (5) |
O2i—Al1—O6 | 174.14 (12) | H51—O5—H52 | 113 (8) |
O3ii—Al1—O6 | 85.43 (11) | Al1—O6—H61 | 115 (5) |
O4iii—Al1—O6 | 89.85 (12) | Al1—O6—H62 | 113 (4) |
O5—Al1—O6 | 83.73 (12) | H61—O6—H62 | 110 (6) |
O1—As1—O2 | 112.10 (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, y−1/2, −z+1/2; (v) −x+1/2, y−1/2, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O5—H51···O4i | 0.82 (8) | 1.78 (8) | 2.592 (3) | 169 (8) |
O5—H52···O1vi | 0.72 (6) | 2.04 (6) | 2.729 (3) | 160 (6) |
O6—H62···O3 | 0.94 (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 formula | Al·AsO4·2(H2O) |
Mr | 201.93 |
Crystal system, space group | Orthorhombic, Pbca |
Temperature (K) | 298 |
a, b, c (Å) | 8.8218 (5), 9.8252 (6), 10.1163 (6) |
V (Å3) | 876.8 (2) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 7.89 |
Crystal size (mm) | 0.08 × 0.08 × 0.08 |
|
Data collection |
Diffractometer | Bruker SMART1000 CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 1999) |
Tmin, Tmax | 0.470, 0.532 |
No. of measured, independent and observed [I > σ(I)] reflections | 8491, 1587, 1059 |
Rint | 0.039 |
(sin θ/λ)max (Å−1) | 0.756 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.025, 0.026, 1.05 |
No. of reflections | 1059 |
No. of parameters | 90 |
No. of restraints | ? |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.73, −0.68 |
Selected geometric parameters (Å, º) topAl1—O1 | 1.903 (2) | Al1—O6 | 1.977 (3) |
Al1—O2i | 1.883 (3) | As1—O1 | 1.684 (2) |
Al1—O3ii | 1.894 (2) | As1—O2 | 1.679 (2) |
Al1—O4iii | 1.866 (3) | As1—O3 | 1.685 (2) |
Al1—O5 | 1.920 (3) | As1—O4 | 1.692 (2) |
| | | |
Al1—O1—As1 | 133.20 (13) | Al1v—O3—As1 | 135.42 (14) |
Al1iv—O2—As1 | 135.50 (15) | Al1iii—O4—As1 | 133.99 (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, y−1/2, −z+1/2; (v) −x+1/2, y−1/2, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O5—H51···O4i | 0.82 (8) | 1.78 (8) | 2.592 (3) | 169 (8) |
O5—H52···O1vi | 0.72 (6) | 2.04 (6) | 2.729 (3) | 160 (6) |
O6—H62···O3 | 0.94 (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. |
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).