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Volume 65 
Part 2 
Pages i6-i7  
February 2009  

Received 3 December 2008
Accepted 29 December 2008
Online 10 January 2009

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Key indicators
Powder Synchrotron study
T = 298 K
Mean [sigma](As-O) = 0.004 Å
Disorder in main residue
R = 0.039
wR = 0.050
Data-to-parameter ratio = 16.63
Details
Open access

Rietveld refinement of a natural cobaltian mansfieldite from synchrotron data

Matteo Zoppia* and Giovanni Pratesib

aMuseo di Storia Naturale - Sezione di Mineralogia, Universitá di Firenze, via La Pira 4, 50121 Firenze, Italy, and bDipartimento di Scienze della Terra, Universitá di Firenze, via La Pira 4, 50121 Firenze, Italy
Correspondence e-mail: matteo.zoppi@unifi.it

A structural refinement of a natural sample of a Co-bearing mansfieldite, AlAsO4·2H2O [aluminium orthoarsenate(V) dihydrate], has been performed based on synchrotron powder diffraction data, with 5% of the octahedral Al sites replaced by Co. Mansfieldite is the aluminium analogue and an isotype of the mineral scorodite (FeAsO4·2H2O), with which it forms a solid solution. The framework structure is based on AsO4 tetrahedra sharing their vertices with AlO4(H2O)2 octahedra. Three of the four H atoms belonging to the two water molecules in cis positions take part in O-H...O hydrogen bonding.

Related literature

Mansfieldite (AlAsO4·2H2O) was first described by Allen et al. (1948[Allen, V. T., Fahey, J. J. & Axelrod, J. M. (1948). Am. Mineral. 33, 122-134.]) and the synthetic analogue was structurally characterised by Harrison (2000[Harrison, W. T. A. (2000). Acta Cryst. C56, e421.]). For the structures of isotypic minerals and synthetic compounds, see: Botelho et al. (1994[Botelho, N. F., Roger, G., d'Yvoire, F., Moëlo, Y. & Volfinger, M. (1994). Eur. J. Mineral. 6, 245-254.]), Tang et al. (2001[Tang, X., Gentiletti, M. J. & Lachgar, A. (2001). J. Chem. Crystallogr. 31, 45-50.]) (yanomamite, InAsO4·2H2O); Kniep et al. (1977[Kniep, R., Mootz, D. & Vegas, A. (1977). Acta Cryst. B33, 263-265.]) (variscite, AlPO4·2H2O); Hawthorne (1976[Hawthorne, F. C. (1976). Acta Cryst. B32, 2891-2892.]), Kitahama et al. (1975[Kitahama, K., Kiriyama, R. & Baba, Y. (1975). Acta Cryst. B31, 322-324.]), Xu et al. (2007[Xu, Y., Zhou, G.-P. & Zheng, X.-F. (2007). Acta Cryst. E63, i67-i69.]) (scorodite, FeAsO4·2H2O); Taxer & Bartl (2004[Taxer, K. & Bartl, H. (2004). Cryst. Res. Technol. 39, 1080-1088.]) (strengite, FePO4·2H2O); Loiseau et al. (1998[Loiseau, T., Paulet, C. & Ferey, G. (1998). C. R. Acad. Sci. Ser. IIc Chim. 1, 667-674.]) (synthetic GaPO4·2H2O); Mooney-Slater (1961[Mooney-Slater, R. C. L. (1961). Acta Cryst. 14, 1140-1146.]) (synthetic InPO4·2H2O and TlPO4·2H2O).

Experimental

Crystal data

  • AlAsO4·2H2O

  • Mr = 203.53

  • Orthorhombic, P b c a

  • a = 8.79263 (11) Å

  • b = 9.79795 (10) Å

  • c = 10.08393 (11) Å

  • V = 868.73 (2) Å3

  • Z = 8

  • Synchrotron radiation

  • [lambda] = 0.68780 Å

  • [mu] = 7.25 mm-1

  • T = 298 K

  • Specimen shape: flat sheet

  • 5.0 × 5.0 × 0.4 mm

  • Particle morphology: powder, light pink
Data collection

  • ESRF BM08 beamline

  • Specimen mounted in transmission mode

  • Scan method: fixed

  • Absorption correction: for a cylinder mounted on the [varphi] axis Tmin = 0.072, Tmax = 0.095

  • 2[theta]min = 6.0, 2[theta]max = 53.0°

  • Increment in 2[theta] = 0.01°
Refinement

  • Rp = 0.039

  • Rwp = 0.050

  • Rexp = 0.039

  • RB = 0.034

  • S = 1.31

  • Excluded region(s): none

  • Profile function: CW pseudo-Voigt

  • 60 parameters

  • No restraints

  • H-atom parameters not refined

  • Preferred orientation correction: Spherical harmonics ODF

Table 1
Selected bond lengths (Å)

Al1-O1 1.908 (4)
Al1-O2i 1.906 (4)
Al1-O3ii 1.850 (4)
Al1-O4iii 1.848 (4)
Al1-O5w 1.914 (4)
Al1-O6w 1.988 (4)
As2-O1 1.676 (3)
As2-O2 1.654 (3)
As2-O3 1.704 (4)
As2-O4 1.682 (4)
Symmetry codes: (i) [-x, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]; (ii) [-x+{\script{1\over 2}}, y+{\script{1\over 2}}, z]; (iii) -x, -y, -z.

Table 2
Hydrogen-bond geometry (Å, °)

D-H...A D-H H...A D...A D-H...A
O5w-H51...O4i 0.83 1.78 2.607 (5) 168 (1)
O5w-H52...O1iv 0.71 2.03 2.614 (5) 161 (1)
O6w-H62...O3 0.93 1.71 2.587 (5) 156 (1)
Symmetry codes: (i) [-x, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]; (iv) [x+{\script{3\over 2}}, y, -z+{\script{3\over 2}}].

Data collection: local image plate reading software; cell refinement: GSAS (Larson & Von Dreele, 2004[Larson, A. C. & Von Dreele, R. B. (2004). GSAS. Report No. LAUR86-748. Los Alamos National Laboratory, New Mexico, USA.]) and EXPGUI (Toby, 2001[Toby, B. H. (2001). J. Appl. Cryst. 34, 210-213.]); data reduction: FIT2D (Hammersley, 1997[Hammersley, A. P. (1997). FIT2D. Internal Report No. ESRF97HA02T. ESRF, Grenoble, France.]); program(s) used to solve structure: atomic coordinates from Harrison (2000[Harrison, W. T. A. (2000). Acta Cryst. C56, e421.]); program(s) used to refine structure: GSAS and EXPGUI; molecular graphics: VICS (Izumi & Dilanian, 2005[Izumi, F. & Dilanian, R. A. (2005). IUCr Commission on Powder Diffraction Newsletter, No. 32, pp. 59-63.]); software used to prepare material for publication: publCIF (Westrip, 2009[Westrip, S. P. (2009). publCIF. In preparation.]).

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WM2209 ).

Acknowledgements

This work was funded by the research grant No. 21403(296) of the University of Florence. We thank Steve Sorrel for supplying the specimen.

References

Allen, V. T., Fahey, J. J. & Axelrod, J. M. (1948). Am. Mineral. 33, 122-134.  [ChemPort]
Botelho, N. F., Roger, G., d'Yvoire, F., Moëlo, Y. & Volfinger, M. (1994). Eur. J. Mineral. 6, 245-254.  [ChemPort]
Hammersley, A. P. (1997). FIT2D. Internal Report No. ESRF97HA02T. ESRF, Grenoble, France.
Harrison, W. T. A. (2000). Acta Cryst. C56, e421.  [CrossRef] [details]
Hawthorne, F. C. (1976). Acta Cryst. B32, 2891-2892.  [CrossRef] [details]
Izumi, F. & Dilanian, R. A. (2005). IUCr Commission on Powder Diffraction Newsletter, No. 32, pp. 59-63.
Kitahama, K., Kiriyama, R. & Baba, Y. (1975). Acta Cryst. B31, 322-324.  [CrossRef] [details]
Kniep, R., Mootz, D. & Vegas, A. (1977). Acta Cryst. B33, 263-265.  [CrossRef] [details] [ISI]
Larson, A. C. & Von Dreele, R. B. (2004). GSAS. Report No. LAUR86-748. Los Alamos National Laboratory, New Mexico, USA.
Loiseau, T., Paulet, C. & Ferey, G. (1998). C. R. Acad. Sci. Ser. IIc Chim. 1, 667-674.  [ChemPort]
Mooney-Slater, R. C. L. (1961). Acta Cryst. 14, 1140-1146.  [CrossRef] [ChemPort] [details]
Tang, X., Gentiletti, M. J. & Lachgar, A. (2001). J. Chem. Crystallogr. 31, 45-50.  [ISI] [CrossRef] [ChemPort]
Taxer, K. & Bartl, H. (2004). Cryst. Res. Technol. 39, 1080-1088.  [ISI] [CrossRef] [ChemPort]
Toby, B. H. (2001). J. Appl. Cryst. 34, 210-213.
Westrip, S. P. (2009). publCIF. In preparation.
Xu, Y., Zhou, G.-P. & Zheng, X.-F. (2007). Acta Cryst. E63, i67-i69.  [CrossRef] [details]

Acta Cryst (2009). E65, i6-i7   [ doi:10.1107/S1600536808044127 ]

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