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Acta Crystallogr Sect E Struct Rep Online. 2008 March 1; 64(Pt 3): i22.
Published online 2008 February 20. doi:  10.1107/S1600536808004492
PMCID: PMC2960788

Reinvestigation of the crystal structure of lautite, CuAsS

Abstract

The crystal structure of the mineral lautite (copper arsenic sulfide), CuAsS, previously described as either centrosymmetric [Pnma; Marumo & Nowacki (1964 [triangle]). Schweiz. Miner. Petro. Mitt. 44, 439–454] or noncentrosymmetric [Pna21; Craig & Stephenson (1965 [triangle]). Acta Cryst. 19, 543–547], was reinvestigated by means of single-crystal X-ray diffraction. The centrosymmetric structural model reported previously was confirmed, although with improved precision for the atomic coordinates and inter­atomic distances. Lautite shows a sphalerite-derivative structure with a linking of Cu[AsS3], As[CuAs2S] and S[Cu3As] tetra­hedra. All atoms lie on special positions (Wyckoff position 4c, site symmetry m).

Related literature

For related literature, see: Craig & Stephenson (1965 [triangle]); Marumo & Nowacki (1964 [triangle]); Wyckoff (1963 [triangle]).

Experimental

Crystal data

  • AsCuS
  • M r = 170.54
  • Orthorhombic, An external file that holds a picture, illustration, etc.
Object name is e-64-00i22-efi7.jpg
  • a = 11.347 (4) Å
  • b = 3.7533 (7) Å
  • c = 5.453 (1) Å
  • V = 232.24 (10) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 24.00 mm−1
  • T = 298 (2) K
  • 0.12 × 0.10 × 0.08 mm

Data collection

  • Bruker P4 diffractometer
  • Absorption correction: ψ scan (North et al., 1968 [triangle]) T min = 0.070, T max = 0.150
  • 3824 measured reflections
  • 574 independent reflections
  • 483 reflections with I > 2σ(I)
  • R int = 0.077
  • 3 standard reflections every 150 reflections intensity decay: none

Refinement

  • R[F 2 > 2σ(F 2)] = 0.046
  • wR(F 2) = 0.108
  • S = 1.09
  • 574 reflections
  • 19 parameters
  • Δρmax = 1.28 e Å−3
  • Δρmin = −1.07 e Å−3

Data collection: XSCANS (Bruker, 1997 [triangle]); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: Xtaldraw (Downs & Hall-Wallace, 2003 [triangle]); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808004492/fi2059sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808004492/fi2059Isup2.hkl

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

Acknowledgments

This work was funded by CNR, Istituto di Geoscienze e Georisorse, Sezione di Firenze.

supplementary crystallographic information

Comment

The crystal structure of lautite was solved by Marumo & Nowacki (1964) in the space group Pnma (R = 9.0%) and by Craig & Stephenson (1965) in the space group Pna21 (R = 13.7%) by means of photographic data and three-dimensional Patterson-function. The low quality of the structural data given by these authors, however, did not allow to obtain an anisotropic model of the structure. Nevertheless, the topologies and interatomic distances of both centrosymmetric and non-centrosymmetric models are very similar.

Although the structural results obtained by Craig & Stephenson (1965) indicate the acentricity of the structure of CuAsS, no clear crystal-chemical reason for the choice of a noncentrosymmetric arrangement was given. To help resolve the concerns relating to the structure of natural lautite, we present new crystal structure data for lautite from its type locality (i.e., Marienberg, Saxony, Germany).

The centrosymmetric structural model previously reported by Marumo & Nowacki (1964) was confirmed, although a higher precision of refinement was achieved (e.s.d. improved by a factor of two) and refinement with anisotropic displacement parameters could be performed (Fig. 1). All atoms lie on special positions (Wyckoff position 4c, site symmetry m). Lautite shows a sphalerite-derivative structure with a linking of Cu[AsS3], As[CuAs2S] and S[Cu3As] tetrahedra (Fig. 2). Within the framework, the As atoms form zigzag As—As chains along [010] exhibiting As—As bond distances [2.4965 (8) Å] and angles [97.48 (4)°] resembling the covalent As—As linkage observed within the sheets of the crystal structure of arsenic (Wyckoff, 1963).

Experimental

A crystal was selected from a natural specimen belonging to the Mineralogical Collection of the Natural History Museum of Florence (catalogue number 44202/G).

Refinement

The crystal structure refinement was performed starting from the atomic coordinates reported by Marumo & Nowacki (1964). Convergence was rapidly obtained for an anisotropic model of the structure.

Figures

Fig. 1.
The crystal structure of lautite down [010]. Displacement parameters are drawn at the 70% probability level. The unit-cell is outlined. Symmetry codes are: (i) -x + 1/2; -y; z + 1/2; (ii) x + 1/2; -y + 1/2; -z + 1/2; (iii) -x; y + 1/2; -z.
Fig. 2.
The crystal structure of lautite showing the linking of Cu[AsS3], As[CuAs2S] and S[Cu3As] tetrahedra. Blu, red and yellow circles indicate Cu, As and S atoms, respectively. The unit-cell is outlined.

Crystal data

AsCuSF000 = 312
Mr = 170.54Dx = 4.878 Mg m3
Orthorhombic, PnmaMo Kα radiation λ = 0.71073 Å
Hall symbol: -P 2ac 2nCell parameters from 38 reflections
a = 11.347 (4) Åθ = 12.5–24.3º
b = 3.7533 (7) ŵ = 24.00 mm1
c = 5.453 (1) ÅT = 298 (2) K
V = 232.24 (10) Å3Block, black
Z = 40.12 × 0.10 × 0.08 mm

Data collection

Bruker P4 diffractometerRint = 0.077
Radiation source: fine-focus sealed tubeθmax = 35.0º
Monochromator: graphiteθmin = 3.6º
T = 298(2) Kh = −18→18
ω scansk = −6→6
Absorption correction: ψ scan(North et al., 1968)l = −8→8
Tmin = 0.070, Tmax = 0.1503 standard reflections
3824 measured reflections every 150 reflections
574 independent reflections intensity decay: none
483 reflections with I > 2σ(I)

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.046  w = 1/[σ2(Fo2) + (0.0856P)2 + 1.9844P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.108(Δ/σ)max < 0.001
S = 1.09Δρmax = 1.28at 0.0736 0.2500 0.3457 (0.68 Å from As) e Å3
574 reflectionsΔρmin = −1.07at 0.0052 0.0883 0.4402 (0.78 Å from As) e Å3
19 parametersExtinction correction: none

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*/Ueq
Cu0.17454 (7)0.25000.06264 (18)0.0165 (2)
As0.01373 (5)0.25000.35177 (11)0.00894 (18)
S0.16576 (12)0.75000.8196 (3)0.0100 (3)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Cu0.0171 (3)0.0168 (4)0.0157 (4)0.000−0.0015 (3)0.000
As0.0105 (3)0.0084 (3)0.0080 (3)0.0000.00083 (17)0.000
S0.0108 (5)0.0114 (5)0.0079 (5)0.000−0.0005 (4)0.000

Geometric parameters (Å, °)

Cu—Si2.2908 (16)As—Asv2.4965 (8)
Cu—Sii2.2996 (10)S—Asiv2.2408 (16)
Cu—Siii2.2996 (10)S—Cuvi2.2908 (16)
Cu—As2.4114 (11)S—Cuvii2.2996 (10)
As—Siv2.2408 (16)S—Cuviii2.2996 (10)
As—Asiv2.4965 (8)
Si—Cu—Sii112.76 (3)Siv—As—Asv99.01 (4)
Si—Cu—Siii112.76 (3)Cu—As—Asv121.19 (3)
Sii—Cu—Siii109.39 (7)Asiv—As—Asv97.48 (4)
Si—Cu—As101.46 (5)Asiv—S—Cuvi117.64 (7)
Sii—Cu—As110.12 (4)Asiv—S—Cuvii106.24 (5)
Siii—Cu—As110.12 (4)Cuvi—S—Cuvii108.56 (4)
Siv—As—Cu114.52 (5)Asiv—S—Cuviii106.24 (5)
Siv—As—Asiv99.01 (4)Cuvi—S—Cuviii108.56 (4)
Cu—As—Asiv121.19 (3)Cuvii—S—Cuviii109.39 (7)

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

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: FI2059).

References

  • Bruker (1997). XSCANS Bruker AXS Inc., Madison, Wisconsin, USA.
  • Craig, D. C. & Stephenson, N. C. (1965). Acta Cryst.19, 543–547.
  • Downs, R. T. & Hall-Wallace, M. (2003). Am. Mineral.88, 247–250.
  • Marumo, F. & Nowacki, W. (1964). Schweiz. Miner. Petro. Mitt.44, 439–454.
  • North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351–359.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Wyckoff, R. W. G. (1963). Crystal Structures, 2nd ed. New York: Interscience Publishers.

Articles from Acta Crystallographica Section E: Structure Reports Online are provided here courtesy of International Union of Crystallography