inorganic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890

Reinvestigation of the crystal structure of lautite, CuAsS

aMuseo di Storia Naturale, Sezione di Mineralogia, Universitá degli Studi di Firenze, Via La Pira 4, I-50121 Firenze, Italy, and bDipartimento di Scienze della Terra, Universitá degli Studi di Firenze, Via La Pira 4, I-50121 Firenze, Italy
*Correspondence e-mail: pbcry@geo.unifi.it

(Received 25 January 2008; accepted 14 February 2008; online 20 February 2008)

The crystal structure of the mineral lautite (copper arsenic sulfide), CuAsS, previously described as either centrosymmetric [Pnma; Marumo & Nowacki (1964[Marumo, F. & Nowacki, W. (1964). Schweiz. Miner. Petro. Mitt. 44, 439-454.]). Schweiz. Miner. Petro. Mitt. 44, 439–454] or noncentrosymmetric [Pna21; Craig & Stephenson (1965[Craig, D. C. & Stephenson, N. C. (1965). Acta Cryst. 19, 543-547.]). 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[Craig, D. C. & Stephenson, N. C. (1965). Acta Cryst. 19, 543-547.]); Marumo & Nowacki (1964[Marumo, F. & Nowacki, W. (1964). Schweiz. Miner. Petro. Mitt. 44, 439-454.]); Wyckoff (1963[Wyckoff, R. W. G. (1963). Crystal Structures, 2nd ed. New York: Interscience Publishers.]).

Experimental

Crystal data
  • AsCuS

  • Mr = 170.54

  • Orthorhombic, P n m a

  • 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[North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351-359.]) Tmin = 0.070, Tmax = 0.150

  • 3824 measured reflections

  • 574 independent reflections

  • 483 reflections with I > 2σ(I)

  • Rint = 0.077

  • 3 standard reflections every 150 reflections intensity decay: none

Refinement
  • R[F2 > 2σ(F2)] = 0.046

  • wR(F2) = 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[Bruker (1997). XSCANS. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: Xtaldraw (Downs & Hall-Wallace, 2003[Downs, R. T. & Hall-Wallace, M. (2003). Am. Mineral. 88, 247-250.]); software used to prepare material for publication: SHELXL97.

Supporting information


Comment top

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).

Related literature top

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

Experimental top

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 top

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.

Computing details top

Data collection: XSCANS (Bruker, 1997); cell refinement: XSCANS (Bruker, 1997); data reduction: XSCANS (Bruker, 1997); 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 (Sheldrick, 2008).

Figures top
[Figure 1] 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.
[Figure 2] 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.
copper arsenic sulfide top
Crystal data top
AsCuSF(000) = 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 = 12.5–24.3°
b = 3.7533 (7) ŵ = 24.00 mm1
c = 5.453 (1) ÅT = 298 K
V = 232.24 (10) Å3Block, black
Z = 40.12 × 0.10 × 0.08 mm
Data collection top
Bruker P4
diffractometer
483 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.077
Graphite monochromatorθmax = 35.0°, θmin = 3.6°
ω scansh = 1818
Absorption correction: ψ scan
(North et al., 1968)
k = 66
Tmin = 0.070, Tmax = 0.150l = 88
3824 measured reflections3 standard reflections every 150 reflections
574 independent reflections intensity decay: none
Refinement top
Refinement on F20 restraints
Least-squares matrix: fullPrimary atom site location: structure-invariant direct methods
R[F2 > 2σ(F2)] = 0.046Secondary atom site location: difference Fourier map
wR(F2) = 0.108 w = 1/[σ2(Fo2) + (0.0856P)2 + 1.9844P]
where P = (Fo2 + 2Fc2)/3
S = 1.09(Δ/σ)max < 0.001
574 reflectionsΔρmax = 1.28 at 0.0736 0.2500 0.3457 (0.68 Å from As) e Å3
19 parametersΔρmin = 1.07 at 0.0052 0.0883 0.4402 (0.78 Å from As) e Å3
Crystal data top
AsCuSV = 232.24 (10) Å3
Mr = 170.54Z = 4
Orthorhombic, PnmaMo Kα radiation
a = 11.347 (4) ŵ = 24.00 mm1
b = 3.7533 (7) ÅT = 298 K
c = 5.453 (1) Å0.12 × 0.10 × 0.08 mm
Data collection top
Bruker P4
diffractometer
483 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.077
Tmin = 0.070, Tmax = 0.1503 standard reflections every 150 reflections
3824 measured reflections intensity decay: none
574 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.04619 parameters
wR(F2) = 0.1080 restraints
S = 1.09Δρmax = 1.28 at 0.0736 0.2500 0.3457 (0.68 Å from As) e Å3
574 reflectionsΔρmin = 1.07 at 0.0052 0.0883 0.4402 (0.78 Å from As) e Å3
Special details top

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) top
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) top
U11U22U33U12U13U23
Cu0.0171 (3)0.0168 (4)0.0157 (4)0.0000.0015 (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)0.0000.0005 (4)0.000
Geometric parameters (Å, º) top
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, z1/2; (ii) x, y1, z1; (iii) x, y, z1; (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.

Experimental details

Crystal data
Chemical formulaAsCuS
Mr170.54
Crystal system, space groupOrthorhombic, Pnma
Temperature (K)298
a, b, c (Å)11.347 (4), 3.7533 (7), 5.453 (1)
V3)232.24 (10)
Z4
Radiation typeMo Kα
µ (mm1)24.00
Crystal size (mm)0.12 × 0.10 × 0.08
Data collection
DiffractometerBruker P4
diffractometer
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.070, 0.150
No. of measured, independent and
observed [I > 2σ(I)] reflections
3824, 574, 483
Rint0.077
(sin θ/λ)max1)0.807
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.046, 0.108, 1.09
No. of reflections574
No. of parameters19
Δρmax, Δρmin (e Å3)1.28 at 0.0736 0.2500 0.3457 (0.68 Å from As), 1.07 at 0.0052 0.0883 0.4402 (0.78 Å from As)

Computer programs: XSCANS (Bruker, 1997), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), Xtaldraw (Downs & Hall-Wallace, 2003).

 

Acknowledgements

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

References

First citationBruker (1997). XSCANS. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationCraig, D. C. & Stephenson, N. C. (1965). Acta Cryst. 19, 543–547.  CrossRef CAS IUCr Journals Web of Science Google Scholar
First citationDowns, R. T. & Hall-Wallace, M. (2003). Am. Mineral. 88, 247–250.  CAS Google Scholar
First citationMarumo, F. & Nowacki, W. (1964). Schweiz. Miner. Petro. Mitt. 44, 439–454.  Google Scholar
First citationNorth, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351–359.  CrossRef IUCr Journals Web of Science Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationWyckoff, R. W. G. (1963). Crystal Structures, 2nd ed. New York: Interscience Publishers.  Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Follow Acta Cryst. E
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds