|Home | About | Journals | Submit | Contact Us | Français|
The crystal structure of the mineral lautite (copper arsenic sulfide), CuAsS, previously described as either centrosymmetric [Pnma; Marumo & Nowacki (1964 ). Schweiz. Miner. Petro. Mitt. 44, 439–454] or noncentrosymmetric [Pna21; Craig & Stephenson (1965 ). 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).
Data collection: XSCANS (Bruker, 1997 ); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ); molecular graphics: Xtaldraw (Downs & Hall-Wallace, 2003 ); software used to prepare material for publication: SHELXL97.
Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808004492/fi2059sup1.cif
Structure factors: contains datablocks I. DOI: 10.1107/S1600536808004492/fi2059Isup2.hkl
This work was funded by CNR, Istituto di Geoscienze e Georisorse, Sezione di Firenze.
A crystal was selected from a natural specimen belonging to the Mineralogical Collection of the Natural History Museum of Florence (catalogue number 44202/G).
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.
|AsCuS||F000 = 312|
|Mr = 170.54||Dx = 4.878 Mg m−3|
|Orthorhombic, Pnma||Mo Kα radiation λ = 0.71073 Å|
|Hall symbol: -P 2ac 2n||Cell parameters from 38 reflections|
|a = 11.347 (4) Å||θ = 12.5–24.3º|
|b = 3.7533 (7) Å||µ = 24.00 mm−1|
|c = 5.453 (1) Å||T = 298 (2) K|
|V = 232.24 (10) Å3||Block, black|
|Z = 4||0.12 × 0.10 × 0.08 mm|
|Bruker P4 diffractometer||Rint = 0.077|
|Radiation source: fine-focus sealed tube||θmax = 35.0º|
|Monochromator: graphite||θmin = 3.6º|
|T = 298(2) K||h = −18→18|
|ω scans||k = −6→6|
|Absorption correction: ψ scan(North et al., 1968)||l = −8→8|
|Tmin = 0.070, Tmax = 0.150||3 standard reflections|
|3824 measured reflections||every 150 reflections|
|574 independent reflections||intensity decay: none|
|483 reflections with I > 2σ(I)|
|Refinement on F2||Primary atom site location: structure-invariant direct methods|
|Least-squares matrix: full||Secondary 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 = 1.09||Δρmax = 1.28at 0.0736 0.2500 0.3457 (0.68 Å from As) e Å−3|
|574 reflections||Δρmin = −1.07at 0.0052 0.0883 0.4402 (0.78 Å from As) e Å−3|
|19 parameters||Extinction correction: none|
|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.|
|Cu||0.17454 (7)||0.2500||0.06264 (18)||0.0165 (2)|
|As||0.01373 (5)||0.2500||0.35177 (11)||0.00894 (18)|
|S||0.16576 (12)||0.7500||0.8196 (3)||0.0100 (3)|
|Cu||0.0171 (3)||0.0168 (4)||0.0157 (4)||0.000||−0.0015 (3)||0.000|
|As||0.0105 (3)||0.0084 (3)||0.0080 (3)||0.000||0.00083 (17)||0.000|
|S||0.0108 (5)||0.0114 (5)||0.0079 (5)||0.000||−0.0005 (4)||0.000|
|Cu—Si||2.2908 (16)||As—Asv||2.4965 (8)|
|Cu—Sii||2.2996 (10)||S—Asiv||2.2408 (16)|
|Cu—Siii||2.2996 (10)||S—Cuvi||2.2908 (16)|
|Cu—As||2.4114 (11)||S—Cuvii||2.2996 (10)|
|As—Siv||2.2408 (16)||S—Cuviii||2.2996 (10)|
|Si—Cu—Sii||112.76 (3)||Siv—As—Asv||99.01 (4)|
|Si—Cu—Siii||112.76 (3)||Cu—As—Asv||121.19 (3)|
|Sii—Cu—Siii||109.39 (7)||Asiv—As—Asv||97.48 (4)|
|Si—Cu—As||101.46 (5)||Asiv—S—Cuvi||117.64 (7)|
|Sii—Cu—As||110.12 (4)||Asiv—S—Cuvii||106.24 (5)|
|Siii—Cu—As||110.12 (4)||Cuvi—S—Cuvii||108.56 (4)|
|Siv—As—Cu||114.52 (5)||Asiv—S—Cuviii||106.24 (5)|
|Siv—As—Asiv||99.01 (4)||Cuvi—S—Cuviii||108.56 (4)|
|Cu—As—Asiv||121.19 (3)||Cuvii—S—Cuviii||109.39 (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.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: FI2059).