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The structure of the orthorhombic room-temperature phase of Cu8GeS6 (copper germanium sulfide), Mr = 773.27, has been refined on the basis of X-ray diffraction data from a 12-fold twinned crystal applying a six-dimensional twin refinement technique. For 1804 unique reflections measured using Mo Kα radiation, RF was 0.083 with 77 structure parameters and 12 scale factors. The symmetry operations, the unit cell and other crystal data are (0, 0, 0; ½, ½, 0) + x, y, z; y, x, z; ¼ − x, ¾ − y, ½ + z; ¾ − y, ¼ − x, ½ + z; a = b = 9.9073 (3) Å, c = 9.8703 (4) Å, α = β = 90°, γ = 90.642 (4)°; V = 968.7 (1) Å3, Z = 4, Dx = 5.358 Mg m−3, μ = 21.70 mm−1. The standard setting of the space group and the reduced unit cell are Pmn21; a = 7.0445 (3), b = 6.9661 (3), c = 9.8699 (5) Å; Z = 2.

Supporting information

cif

Crystallographic Information File (CIF)
Contains datablock Cu8GeS6-2

sft

Structure factor file (SHELXL table format)
Supplementary material

Computing details top

Program(s) used to refine structure: FMLSM V.3.20 (Kato, 1998).

Figures top
[Figure 1]
[Figure 2]
(Cu8GeS6-2) top
Crystal data top
Cu8GeS6The structural model can be described based on Pmn21 with lattice constants A=7.0445(3), B=6.9661(3), C=9.8699(5). For the structure refinement, new basis a=A+B, b=B-A, c=C are selected. The new cell is C-centered, and cell constants are a=b=9.9073(3), c=9.8703(4), α=β=90, χ=90.624(4). Symmetry operations based on a, b, and c are listed as symmetry equiv pos as xyz.
Mr = 773.27Dx = 5.358 Mg m3
Orthorhombic, Pmn21Mo Kα radiation, λ = 0.70930 Å
Hall symbol: P 2ac -2Cell parameters from 25 reflections
a = 9.9073 (3) Åθ = 15–22.5°
b = 9.9073 ŵ = 21.70 mm1
c = 9.8703 (4) ÅT = 293 K
V = 968.7 (1) Å3Plate-like, gray
Z = 40.18 × 0.12 × 0.08 mm
Data collection top
Enraf-Nonius CAD4
diffractometer
1805 reflections with I > 2σ(I)
Radiation source: xray tubeRint = 0.054
Graphite monochromatorθmax = 34.8°, θmin = 3.6°
ω–2θ scansh = 019
Absorption correction: gaussian
?
k = 019
Tmin = 0.10, Tmax = 0.23l = 2727
9341 measured reflections3 standard reflections every 200 reflections
9341 independent reflections intensity decay: none
Refinement top
Refinement on F89 parameters
Least-squares matrix: full0 restraints
R[F2 > 2σ(F2)] = 0.087Calculated w = 1
wR(F2) = .094(Δ/σ)max = 0.001
1805 reflections
Crystal data top
Cu8GeS6V = 968.7 (1) Å3
Mr = 773.27Z = 4
Orthorhombic, Pmn21Mo Kα radiation
a = 9.9073 (3) ŵ = 21.70 mm1
b = 9.9073 ÅT = 293 K
c = 9.8703 (4) Å0.18 × 0.12 × 0.08 mm
Data collection top
Enraf-Nonius CAD4
diffractometer
1805 reflections with I > 2σ(I)
Absorption correction: gaussian
?
Rint = 0.054
Tmin = 0.10, Tmax = 0.233 standard reflections every 200 reflections
9341 measured reflections intensity decay: none
9341 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.08789 parameters
wR(F2) = .0940 restraints
1805 reflections
Special details top

Refinement. Observed reflections seem to be caused by a twinned pseudo-cubic crystal, composing of the major group with hkl and the minor group with h'k'l'. The twin operations of the symmetry equivalent position as x,y,z for the major group are respectively x,y,z, y,z,x, z,x,y, x,-y,-z, -y,-z,x and -z,x,-y. To assign integral indexes to all of the major and minor groups, a six-dimensional formalism is applied. The major group is assigned hkl000, while the minor group is assigned by 000h'k'l'. Symmetry operations are also expressed in the (3 + 3)-dimensional formalism using the space-group operations, the twin operations for the six major domains and the six-dimensional twin operation·(Kato, K., Acta Cryst.(1994) A50, 351–357, Z. Krist. (1997) 212, 423–427) Refinement was performed through a version V3.20 of FMLSM (Kato). Besides structral parameters, 12 scale factors were considered as parameters, because the volumes of the six major and six minor domains are proportional to the square of the scale factors. Atomic coordinates X,Y,Z based on the orthorhombic cell with a space group Pmn21 and cell parameters A=7.0445 (3), B=6.9661 (3), C=9.8699 (5) can be calculated from the values of x,y,z using the relations X=x-y, Y=x + y and Z=z.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Ge0.1246 (2)0.12460.5072 (13)0.009 (1)
Cu10.3677 (4)0.1567 (4)0.2566 (15)0.025 (1)
Cu20.1533 (5)0.0457 (4)0.8512 (14)0.029 (1)
Cu30.1735 (7)0.0268 (5)0.1494 (14)0.049 (2)
Cu40.3005 (5)0.30050.0173 (17)0.033 (2)
Cu50.3646 (5)0.36460.4759 (15)0.024 (2)
S10.4991 (7)0.2573 (6)0.8864 (16)0.012 (2)
S20.0001 (7)0.00010.6440 (18)0.009 (2)
S30.2488 (7)0.24880.6402 (17)0.008 (2)
S40.3875 (6)0.38750.251 (2)0.019 (3)
S50.1357 (6)0.13570.00.011 (2)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ge0.005 (1)0.0050.018 (3)0.003 (1)0.001 (1)0.001
Cu10.027 (2)0.015 (1)0.033 (3)0.002 (2)0.011 (2)0.001 (2)
Cu20.034 (2)0.022 (2)0.030 (3)0.003 (2)0.003 (2)0.006 (2)
Cu30.091 (5)0.024 (2)0.032 (3)0.019 (3)0.009 (3)0.008 (2)
Cu40.023 (2)0.0230.054 (5)0.009 (2)0.012 (3)0.012
Cu50.028 (2)0.0280.016 (4)0.012 (3)0.005 (2)0.005
S10.010 (3)0.009 (3)0.017 (5)0.004 (3)0.002 (2)0.002 (2)
S20.008 (2)0.0080.013 (5)0.002 (3)0.002 (3)0.002
S30.006 (2)0.0060.013 (5)0.002 (3)0.003 (3)0.003
S40.008 (2)0.0080.040 (8)0.002 (3)0.006 (3)0.006
S50.008 (2)0.0080.018 (6)0.007 (3)0.000 (2)0.000
Geometric parameters (Å, º) top
Ge—S1i2.175 (7)Cu3—S2vi2.345 (7)
Ge—S1ii2.175 (7)Cu3—S52.219 (10)
Ge—S22.201 (11)Cu4—S1vii2.396 (11)
Ge—S32.172 (10)Cu4—S1viii2.396 (11)
S1i—S1ii3.638 (12)Cu4—S42.609 (19)
S2—S1i3.558 (12)Cu4—S52.302 (11)
S2—S1ii3.558 (12)Cu5—S2ix2.512 (15)
S3—S1i3.566 (12)Cu5—S32.288 (15)
S3—S1ii3.566 (12)Cu5—S42.238 (19)
S2—S33.468 (17)Cu1—Cu2ii2.801 (7)
Cu1—S1ii2.363 (9)Cu1—Cu32.837 (9)
Cu1—S3ii2.343 (8)Cu1—Cu42.841 (9)
Cu1—S42.294 (8)Cu2—Cu2ix2.804 (9)
Cu2—S1iii2.489 (9)Cu2—Cu3x2.758 (7)
Cu2—S22.590 (13)Cu2—Cu5iv2.702 (7)
Cu2—S4iv2.477 (9)Cu3—Cu3ix2.823 (12)
Cu2—S5v2.329 (11)Cu3—Cu5ii2.853 (9)
Cu3—S1ii2.469 (13)
S1—Ge—S1113.5 (6)S1—Ge—S3108.8 (3)
S1—Ge—S3110.2 (3)S1—Ge—S1105.0 (6)
Symmetry codes: (i) y+1/4, x+3/4, z1/2; (ii) x+3/4, y+1/4, z1/2; (iii) x1/2, y1/2, z; (iv) x+3/4, y+1/4, z+1/2; (v) x, y, z+1; (vi) y+1/4, x1/4, z1/2; (vii) x, y, z1; (viii) y, x, z1; (ix) x+1/2, y+1/2, z; (x) y+1/4, x1/4, z+1/2.

Experimental details

Crystal data
Chemical formulaCu8GeS6
Mr773.27
Crystal system, space groupOrthorhombic, Pmn21
Temperature (K)293
a, b, c (Å)9.9073 (3), 9.9073, 9.8703 (4)
V3)968.7 (1)
Z4
Radiation typeMo Kα
µ (mm1)21.70
Crystal size (mm)0.18 × 0.12 × 0.08
Data collection
DiffractometerEnraf-Nonius CAD4
diffractometer
Absorption correctionGaussian
Tmin, Tmax0.10, 0.23
No. of measured, independent and
observed [I > 2σ(I)] reflections
9341, 9341, 1805
Rint0.054
(sin θ/λ)max1)0.804
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.087, .094, ?
No. of reflections1805
No. of parameters89
Δρmax, Δρmin (e Å3)?, ?

Computer programs: FMLSM V.3.20 (Kato, 1998).

Selected geometric parameters (Å, º) top
Ge—S1i2.175 (7)Cu3—S2vi2.345 (7)
Ge—S1ii2.175 (7)Cu3—S52.219 (10)
Ge—S22.201 (11)Cu4—S1vii2.396 (11)
Ge—S32.172 (10)Cu4—S1viii2.396 (11)
S1i—S1ii3.638 (12)Cu4—S42.609 (19)
S2—S1i3.558 (12)Cu4—S52.302 (11)
S2—S1ii3.558 (12)Cu5—S2ix2.512 (15)
S3—S1i3.566 (12)Cu5—S32.288 (15)
S3—S1ii3.566 (12)Cu5—S42.238 (19)
S2—S33.468 (17)Cu1—Cu2ii2.801 (7)
Cu1—S1ii2.363 (9)Cu1—Cu32.837 (9)
Cu1—S3ii2.343 (8)Cu1—Cu42.841 (9)
Cu1—S42.294 (8)Cu2—Cu2ix2.804 (9)
Cu2—S1iii2.489 (9)Cu2—Cu3x2.758 (7)
Cu2—S22.590 (13)Cu2—Cu5iv2.702 (7)
Cu2—S4iv2.477 (9)Cu3—Cu3ix2.823 (12)
Cu2—S5v2.329 (11)Cu3—Cu5ii2.853 (9)
Cu3—S1ii2.469 (13)
S1—Ge—S1113.5 (6)S1—Ge—S3108.8 (3)
S1—Ge—S3110.2 (3)S1—Ge—S1105.0 (6)
Symmetry codes: (i) y+1/4, x+3/4, z1/2; (ii) x+3/4, y+1/4, z1/2; (iii) x1/2, y1/2, z; (iv) x+3/4, y+1/4, z+1/2; (v) x, y, z+1; (vi) y+1/4, x1/4, z1/2; (vii) x, y, z1; (viii) y, x, z1; (ix) x+1/2, y+1/2, z; (x) y+1/4, x1/4, z+1/2.
 
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