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Rare-earth metal coinage-metal diarsenides LnTAs2 (Ln = Y, La, Ce–Lu; T = Cu, Ag, Au) are known to crystallize in structures closely related to the HfCuSi2 type, which comprises a stacking sequence of puckered TAs layers and planar square As nets, separated by the Ln atoms. CeAu1−δAs2, with δ = 0.015 (2), shows an incommensurate positional modulation of the arsenic atoms in the planar As nets. Based on X-ray diffraction data on a twinned crystal, a structure model in the monoclinic superspace group P121/m1(α0γ)00 (No. 11.1) with basic unit-cell parameters of a = 5.804 (1), b = 5.814 (1), c = 10.179 (1) Å and β = 90.09 (8)° is presented. The components of the modulation wavevector q = αa* + 0b* + γc* are α = 0.08 (1) and γ = 0.39 (1). The structure comprises cistrans chains and rectangles of As atoms and displays an intricate stacking sequence of the modulated arsenic nets. Rod groups and layer groups of the respective arrangements are identified and the arrangement of different motifs of the modulated As net is discussed.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768109026986/ck5035sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108768109026986/ck5035Isup2.hkl
Contains datablock I

Computing details top

Data collection: X-AREA, STOE, 2006; cell refinement: X-AREA, STOE, 2006; data reduction: X-AREA, STOE, 2002; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: Jana2000 (Petricek, Dusek & Palatinus, 2000); molecular graphics: DIAMOND-Visuelles Informationssystem für Kristallstrukturen (G. Bergerhoff, Bonn, 1999); software used to prepare material for publication: Jana2000 (Petricek, Dusek & Palatinus, 2000).

Figures top
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[Figure 11]
(I) top
Crystal data top
As2AuCeZ = 4
Mr = 486.93F(000) = 808
Monoclinic, P21/m(α0γ)00†Dx = 9.41 Mg m3
q = 0.08000a* + -0.38890c*Mo Kα radiation, λ = 0.71073 Å
a = 5.8040 (1) ŵ = 74.55 mm1
b = 5.8140 (1) ÅT = 293 K
c = 10.1790 (1) Å, black
β = 90.09 (8)°0.14 × 0.14 × 0.004 mm
V = 343.48 (9) Å3
† Symmetry operations: (1) x1, x2, x3, x4; (2) −x1, 1/2+x2, −x3, −x4; (3) −x1, −x2, −x3, −x4; (4) x1, 1/2−x2, x3, x4.

Data collection top
STOE IPDS 2
diffractometer
4210 independent reflections
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus1422 reflections with I > 3σ(I)
Plane graphite monochromatorRint = 0.068
Detector resolution: 6.67 pixels mm-1θmax = 33.5°, θmin = 2.8°
ω scansh = 99
Absorption correction: numerical
(Jana2000; Petricek, Dusek & Palatinus, 2000)
k = 88
Tmin = 0.015, Tmax = 0.306l = 1614
20909 measured reflections
Refinement top
Refinement on FWeighting scheme based on measured s.u.'s w = 1/(σ2(F) + 0.0001F2)
R[F2 > 2σ(F2)] = 0.034(Δ/σ)max = 0.041
wR(F2) = 0.040Δρmax = 2.49 e Å3
S = 1.25Δρmin = 2.29 e Å3
4210 reflectionsExtinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974)
134 parametersExtinction coefficient: 0.53 (2)
Crystal data top
As2AuCeβ = 90.09 (8)°
Mr = 486.93V = 343.48 (9) Å3
Monoclinic, P21/m(α0γ)00†Z = 4
q = 0.08000a* + -0.38890c*Mo Kα radiation
a = 5.8040 (1) ŵ = 74.55 mm1
b = 5.8140 (1) ÅT = 293 K
c = 10.1790 (1) Å0.14 × 0.14 × 0.004 mm
† Symmetry operations: (1) x1, x2, x3, x4; (2) −x1, 1/2+x2, −x3, −x4; (3) −x1, −x2, −x3, −x4; (4) x1, 1/2−x2, x3, x4.

Data collection top
STOE IPDS 2
diffractometer
4210 independent reflections
Absorption correction: numerical
(Jana2000; Petricek, Dusek & Palatinus, 2000)
1422 reflections with I > 3σ(I)
Tmin = 0.015, Tmax = 0.306Rint = 0.068
20909 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.034134 parameters
wR(F2) = 0.040Δρmax = 2.49 e Å3
S = 1.25Δρmin = 2.29 e Å3
4210 reflections
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Ce10.0005 (4)0.250.23003 (4)0.01262 (12)
Ce20.5001 (4)0.750.24019 (4)0.01220 (13)
Au10.24822 (4)0.0005 (2)0.49929 (10)0.01869 (7)0.9858 (17)
As10.9978 (6)0.250.68044 (9)0.0142 (2)
As20.4991 (6)0.750.67811 (8)0.0141 (2)
As30.27901 (14)0.0038 (6)0.0001 (3)0.02084 (18)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ce10.0136 (2)0.0104 (2)0.0139 (2)00.0004 (8)0
Ce20.0142 (2)0.0101 (2)0.0122 (2)00.0019 (9)0
Au10.02132 (13)0.01698 (10)0.01778 (11)0.0024 (3)0.0011 (7)0.00082 (10)
As10.0140 (4)0.0106 (3)0.0179 (4)00.0090 (12)0
As20.0142 (4)0.0111 (3)0.0169 (4)00.0079 (12)0
As30.0148 (3)0.0352 (4)0.0124 (2)0.0049 (9)0.0025 (11)0.0019 (3)
Bond lengths (Å) top
AverageMinimumMaximum
Ce1—Au13.419 (3)3.389 (3)3.449 (3)
Ce1—Au1i3.434 (3)3.418 (3)3.450 (3)
Ce1—Au1ii3.434 (3)3.418 (3)3.450 (3)
Ce1—Au1iii3.419 (3)3.389 (3)3.449 (3)
Ce1—As1iv3.0465 (14)3.0416 (14)3.0515 (14)
Ce1—As1v3.0465 (14)3.0416 (14)3.0515 (14)
Ce1—As2vi3.048 (5)3.024 (5)3.071 (5)
Ce1—As2v3.050 (5)3.040 (5)3.060 (5)
Ce1—As33.207 (4)3.177 (5)3.237 (5)
Ce1—As3vii3.187 (4)3.159 (5)3.217 (5)
Ce1—As3viii3.187 (4)3.159 (5)3.217 (5)
Ce1—As3iii3.207 (4)3.177 (5)3.237 (5)
Ce2—Au1ix3.348 (3)3.312 (3)3.385 (3)
Ce2—Au1v3.358 (3)3.344 (3)3.373 (3)
Ce2—Au1x3.358 (3)3.344 (3)3.373 (3)
Ce2—Au1iii3.348 (3)3.312 (3)3.385 (3)
Ce2—As1v3.002 (5)2.974 (5)3.029 (5)
Ce2—As1xi3.023 (5)3.012 (5)3.034 (5)
Ce2—As2v3.0237 (13)3.0186 (12)3.0287 (13)
Ce2—As2xii3.0237 (13)3.0186 (12)3.0287 (13)
Ce2—As3ix3.107 (4)3.065 (5)3.151 (5)
Ce2—As3xiii3.134 (4)3.080 (5)3.188 (5)
Ce2—As3xiv3.134 (4)3.080 (5)3.188 (5)
Ce2—As3iii3.107 (4)3.065 (5)3.151 (5)
Au1—Au1i2.8815 (18)2.870 (3)2.893 (3)
Au1—Au1iv2.9227 (18)2.913 (3)2.932 (3)
Au1—Au1xv2.901 (2)2.889 (2)2.914 (2)
Au1—Au1iii2.913 (2)2.900 (2)2.925 (2)
Au1—As1xvi2.765 (4)2.735 (4)2.795 (4)
Au1—As1iv2.735 (4)2.718 (4)2.753 (4)
Au1—As2xvii2.744 (4)2.720 (4)2.767 (4)
Au1—As2v2.747 (4)2.719 (4)2.773 (4)
As3—As3vii3.241 (5)3.211 (6)3.275 (6)
As3—As3xviii2.569 (5)2.519 (6)2.623 (6)
As3—As3xv2.861 (6)2.699 (5)3.026 (5)
As3—As3iii2.953 (6)2.788 (5)3.115 (5)
Symmetry codes: (i) x1, x2, x3+1, x4; (ii) x1, x2+1/2, x3+1, x4; (iii) x1, x2+1/2, x3, x4; (iv) x1+1, x2, x3+1, x4; (v) x1+1, x2+1, x3+1, x4; (vi) x1, x2+1, x3+1, x4; (vii) x1, x2, x3, x4; (viii) x1, x2+1/2, x3, x4; (ix) x1, x2+1, x3, x4; (x) x1+1, x2+1/2, x3+1, x4; (xi) x1+2, x2+1, x3+1, x4; (xii) x1+1, x2+2, x3+1, x4; (xiii) x1+1, x2+1, x3, x4; (xiv) x1+1, x2+1/2, x3, x4; (xv) x1, x21/2, x3, x4; (xvi) x11, x2, x3, x4; (xvii) x1, x21, x3, x4; (xviii) x1+1, x2, x3, x4.

Experimental details

Crystal data
Chemical formulaAs2AuCe
Mr486.93
Crystal system, space groupMonoclinic, P21/m(α0γ)00†
Temperature (K)293
Wave vectorsq = 0.08000a* + -0.38890c*
a, b, c (Å)5.8040 (1), 5.8140 (1), 10.1790 (1)
β (°) 90.09 (8)
V3)343.48 (9)
Z4
Radiation typeMo Kα
µ (mm1)74.55
Crystal size (mm)0.14 × 0.14 × 0.004
Data collection
DiffractometerSTOE IPDS 2
diffractometer
Absorption correctionNumerical
(Jana2000; Petricek, Dusek & Palatinus, 2000)
Tmin, Tmax0.015, 0.306
No. of measured, independent and
observed [I > 3σ(I)] reflections
20909, 4210, 1422
Rint0.068
(sin θ/λ)max1)0.776
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.034, 0.040, 1.25
No. of reflections4210
No. of parameters134
No. of restraints?
Δρmax, Δρmin (e Å3)2.49, 2.29

† Symmetry operations: (1) x1, x2, x3, x4; (2) −x1, 1/2+x2, −x3, −x4; (3) −x1, −x2, −x3, −x4; (4) x1, 1/2−x2, x3, x4.

Computer programs: X-AREA, STOE, 2006, X-AREA, STOE, 2002, SHELXS97 (Sheldrick, 1997), Jana2000 (Petricek, Dusek & Palatinus, 2000), DIAMOND-Visuelles Informationssystem für Kristallstrukturen (G. Bergerhoff, Bonn, 1999).

Selected bond lengths (Å) top
AverageMinimumMaximum
Ce1—Au13.419 (3)3.389 (3)3.449 (3)
Ce1—Au1i3.434 (3)3.418 (3)3.450 (3)
Ce1—Au1ii3.434 (3)3.418 (3)3.450 (3)
Ce1—Au1iii3.419 (3)3.389 (3)3.449 (3)
Ce1—As1iv3.0465 (14)3.0416 (14)3.0515 (14)
Ce1—As1v3.0465 (14)3.0416 (14)3.0515 (14)
Ce1—As2vi3.048 (5)3.024 (5)3.071 (5)
Ce1—As2v3.050 (5)3.040 (5)3.060 (5)
Ce1—As33.207 (4)3.177 (5)3.237 (5)
Ce1—As3vii3.187 (4)3.159 (5)3.217 (5)
Ce1—As3viii3.187 (4)3.159 (5)3.217 (5)
Ce1—As3iii3.207 (4)3.177 (5)3.237 (5)
Ce2—Au1ix3.348 (3)3.312 (3)3.385 (3)
Ce2—Au1v3.358 (3)3.344 (3)3.373 (3)
Ce2—Au1x3.358 (3)3.344 (3)3.373 (3)
Ce2—Au1iii3.348 (3)3.312 (3)3.385 (3)
Ce2—As1v3.002 (5)2.974 (5)3.029 (5)
Ce2—As1xi3.023 (5)3.012 (5)3.034 (5)
Ce2—As2v3.0237 (13)3.0186 (12)3.0287 (13)
Ce2—As2xii3.0237 (13)3.0186 (12)3.0287 (13)
Ce2—As3ix3.107 (4)3.065 (5)3.151 (5)
Ce2—As3xiii3.134 (4)3.080 (5)3.188 (5)
Ce2—As3xiv3.134 (4)3.080 (5)3.188 (5)
Ce2—As3iii3.107 (4)3.065 (5)3.151 (5)
Au1—Au1i2.8815 (18)2.870 (3)2.893 (3)
Au1—Au1iv2.9227 (18)2.913 (3)2.932 (3)
Au1—Au1xv2.901 (2)2.889 (2)2.914 (2)
Au1—Au1iii2.913 (2)2.900 (2)2.925 (2)
Au1—As1xvi2.765 (4)2.735 (4)2.795 (4)
Au1—As1iv2.735 (4)2.718 (4)2.753 (4)
Au1—As2xvii2.744 (4)2.720 (4)2.767 (4)
Au1—As2v2.747 (4)2.719 (4)2.773 (4)
As3—As3vii3.241 (5)3.211 (6)3.275 (6)
As3—As3xviii2.569 (5)2.519 (6)2.623 (6)
As3—As3xv2.861 (6)2.699 (5)3.026 (5)
As3—As3iii2.953 (6)2.788 (5)3.115 (5)
Symmetry codes: (i) x1, x2, x3+1, x4; (ii) x1, x2+1/2, x3+1, x4; (iii) x1, x2+1/2, x3, x4; (iv) x1+1, x2, x3+1, x4; (v) x1+1, x2+1, x3+1, x4; (vi) x1, x2+1, x3+1, x4; (vii) x1, x2, x3, x4; (viii) x1, x2+1/2, x3, x4; (ix) x1, x2+1, x3, x4; (x) x1+1, x2+1/2, x3+1, x4; (xi) x1+2, x2+1, x3+1, x4; (xii) x1+1, x2+2, x3+1, x4; (xiii) x1+1, x2+1, x3, x4; (xiv) x1+1, x2+1/2, x3, x4; (xv) x1, x21/2, x3, x4; (xvi) x11, x2, x3, x4; (xvii) x1, x21, x3, x4; (xviii) x1+1, x2, x3, x4.
 

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