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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 cis–trans 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
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).
Crystal data top
As2AuCe | Z = 4 |
Mr = 486.93 | F(000) = 808 |
Monoclinic, P21/m(α0γ)00† | Dx = 9.41 Mg m−3 |
q = 0.08000a* + -0.38890c* | Mo Kα radiation, λ = 0.71073 Å |
a = 5.8040 (1) Å | µ = 74.55 mm−1 |
b = 5.8140 (1) Å | T = 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 focus | 1422 reflections with I > 3σ(I) |
Plane graphite monochromator | Rint = 0.068 |
Detector resolution: 6.67 pixels mm-1 | θmax = 33.5°, θmin = 2.8° |
ω scans | h = −9→9 |
Absorption correction: numerical (Jana2000; Petricek, Dusek & Palatinus, 2000) | k = −8→8 |
Tmin = 0.015, Tmax = 0.306 | l = −16→14 |
20909 measured reflections | |
Refinement top
Refinement on F | Weighting 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) = 0.040 | Δρmax = 2.49 e Å−3 |
S = 1.25 | Δρmin = −2.29 e Å−3 |
4210 reflections | Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974) |
134 parameters | Extinction coefficient: 0.53 (2) |
Crystal data top
As2AuCe | β = 90.09 (8)° |
Mr = 486.93 | V = 343.48 (9) Å3 |
Monoclinic, P21/m(α0γ)00† | Z = 4 |
q = 0.08000a* + -0.38890c* | Mo Kα radiation |
a = 5.8040 (1) Å | µ = 74.55 mm−1 |
b = 5.8140 (1) Å | T = 293 K |
c = 10.1790 (1) Å | 0.14 × 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 = 0.306 | Rint = 0.068 |
20909 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.034 | 134 parameters |
wR(F2) = 0.040 | Δρmax = 2.49 e Å−3 |
S = 1.25 | Δρmin = −2.29 e Å−3 |
4210 reflections | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Ce1 | 0.0005 (4) | 0.25 | 0.23003 (4) | 0.01262 (12) | |
Ce2 | 0.5001 (4) | 0.75 | 0.24019 (4) | 0.01220 (13) | |
Au1 | 0.24822 (4) | −0.0005 (2) | 0.49929 (10) | 0.01869 (7) | 0.9858 (17) |
As1 | 0.9978 (6) | 0.25 | 0.68044 (9) | 0.0142 (2) | |
As2 | 0.4991 (6) | 0.75 | 0.67811 (8) | 0.0141 (2) | |
As3 | 0.27901 (14) | −0.0038 (6) | 0.0001 (3) | 0.02084 (18) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Ce1 | 0.0136 (2) | 0.0104 (2) | 0.0139 (2) | 0 | 0.0004 (8) | 0 |
Ce2 | 0.0142 (2) | 0.0101 (2) | 0.0122 (2) | 0 | −0.0019 (9) | 0 |
Au1 | 0.02132 (13) | 0.01698 (10) | 0.01778 (11) | −0.0024 (3) | −0.0011 (7) | −0.00082 (10) |
As1 | 0.0140 (4) | 0.0106 (3) | 0.0179 (4) | 0 | −0.0090 (12) | 0 |
As2 | 0.0142 (4) | 0.0111 (3) | 0.0169 (4) | 0 | −0.0079 (12) | 0 |
As3 | 0.0148 (3) | 0.0352 (4) | 0.0124 (2) | 0.0049 (9) | −0.0025 (11) | −0.0019 (3) |
Bond lengths (Å) top | Average | Minimum | Maximum |
Ce1—Au1 | 3.419 (3) | 3.389 (3) | 3.449 (3) |
Ce1—Au1i | 3.434 (3) | 3.418 (3) | 3.450 (3) |
Ce1—Au1ii | 3.434 (3) | 3.418 (3) | 3.450 (3) |
Ce1—Au1iii | 3.419 (3) | 3.389 (3) | 3.449 (3) |
Ce1—As1iv | 3.0465 (14) | 3.0416 (14) | 3.0515 (14) |
Ce1—As1v | 3.0465 (14) | 3.0416 (14) | 3.0515 (14) |
Ce1—As2vi | 3.048 (5) | 3.024 (5) | 3.071 (5) |
Ce1—As2v | 3.050 (5) | 3.040 (5) | 3.060 (5) |
Ce1—As3 | 3.207 (4) | 3.177 (5) | 3.237 (5) |
Ce1—As3vii | 3.187 (4) | 3.159 (5) | 3.217 (5) |
Ce1—As3viii | 3.187 (4) | 3.159 (5) | 3.217 (5) |
Ce1—As3iii | 3.207 (4) | 3.177 (5) | 3.237 (5) |
Ce2—Au1ix | 3.348 (3) | 3.312 (3) | 3.385 (3) |
Ce2—Au1v | 3.358 (3) | 3.344 (3) | 3.373 (3) |
Ce2—Au1x | 3.358 (3) | 3.344 (3) | 3.373 (3) |
Ce2—Au1iii | 3.348 (3) | 3.312 (3) | 3.385 (3) |
Ce2—As1v | 3.002 (5) | 2.974 (5) | 3.029 (5) |
Ce2—As1xi | 3.023 (5) | 3.012 (5) | 3.034 (5) |
Ce2—As2v | 3.0237 (13) | 3.0186 (12) | 3.0287 (13) |
Ce2—As2xii | 3.0237 (13) | 3.0186 (12) | 3.0287 (13) |
Ce2—As3ix | 3.107 (4) | 3.065 (5) | 3.151 (5) |
Ce2—As3xiii | 3.134 (4) | 3.080 (5) | 3.188 (5) |
Ce2—As3xiv | 3.134 (4) | 3.080 (5) | 3.188 (5) |
Ce2—As3iii | 3.107 (4) | 3.065 (5) | 3.151 (5) |
Au1—Au1i | 2.8815 (18) | 2.870 (3) | 2.893 (3) |
Au1—Au1iv | 2.9227 (18) | 2.913 (3) | 2.932 (3) |
Au1—Au1xv | 2.901 (2) | 2.889 (2) | 2.914 (2) |
Au1—Au1iii | 2.913 (2) | 2.900 (2) | 2.925 (2) |
Au1—As1xvi | 2.765 (4) | 2.735 (4) | 2.795 (4) |
Au1—As1iv | 2.735 (4) | 2.718 (4) | 2.753 (4) |
Au1—As2xvii | 2.744 (4) | 2.720 (4) | 2.767 (4) |
Au1—As2v | 2.747 (4) | 2.719 (4) | 2.773 (4) |
As3—As3vii | 3.241 (5) | 3.211 (6) | 3.275 (6) |
As3—As3xviii | 2.569 (5) | 2.519 (6) | 2.623 (6) |
As3—As3xv | 2.861 (6) | 2.699 (5) | 3.026 (5) |
As3—As3iii | 2.953 (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, −x2−1/2, x3, x4; (xvi) x1−1, x2, x3, x4; (xvii) x1, x2−1, x3, x4; (xviii) −x1+1, −x2, −x3, −x4. |
Experimental details
Crystal data |
Chemical formula | As2AuCe |
Mr | 486.93 |
Crystal system, space group | Monoclinic, P21/m(α0γ)00† |
Temperature (K) | 293 |
Wave vectors | q = 0.08000a* + -0.38890c* |
a, b, c (Å) | 5.8040 (1), 5.8140 (1), 10.1790 (1) |
β (°) | 90.09 (8) |
V (Å3) | 343.48 (9) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 74.55 |
Crystal size (mm) | 0.14 × 0.14 × 0.004 |
|
Data collection |
Diffractometer | STOE IPDS 2 diffractometer |
Absorption correction | Numerical (Jana2000; Petricek, Dusek & Palatinus, 2000) |
Tmin, Tmax | 0.015, 0.306 |
No. of measured, independent and observed [I > 3σ(I)] reflections | 20909, 4210, 1422 |
Rint | 0.068 |
(sin θ/λ)max (Å−1) | 0.776 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.034, 0.040, 1.25 |
No. of reflections | 4210 |
No. of parameters | 134 |
No. of restraints | ? |
Δρmax, Δρmin (e Å−3) | 2.49, −2.29 |
Selected bond lengths (Å) top | Average | Minimum | Maximum |
Ce1—Au1 | 3.419 (3) | 3.389 (3) | 3.449 (3) |
Ce1—Au1i | 3.434 (3) | 3.418 (3) | 3.450 (3) |
Ce1—Au1ii | 3.434 (3) | 3.418 (3) | 3.450 (3) |
Ce1—Au1iii | 3.419 (3) | 3.389 (3) | 3.449 (3) |
Ce1—As1iv | 3.0465 (14) | 3.0416 (14) | 3.0515 (14) |
Ce1—As1v | 3.0465 (14) | 3.0416 (14) | 3.0515 (14) |
Ce1—As2vi | 3.048 (5) | 3.024 (5) | 3.071 (5) |
Ce1—As2v | 3.050 (5) | 3.040 (5) | 3.060 (5) |
Ce1—As3 | 3.207 (4) | 3.177 (5) | 3.237 (5) |
Ce1—As3vii | 3.187 (4) | 3.159 (5) | 3.217 (5) |
Ce1—As3viii | 3.187 (4) | 3.159 (5) | 3.217 (5) |
Ce1—As3iii | 3.207 (4) | 3.177 (5) | 3.237 (5) |
Ce2—Au1ix | 3.348 (3) | 3.312 (3) | 3.385 (3) |
Ce2—Au1v | 3.358 (3) | 3.344 (3) | 3.373 (3) |
Ce2—Au1x | 3.358 (3) | 3.344 (3) | 3.373 (3) |
Ce2—Au1iii | 3.348 (3) | 3.312 (3) | 3.385 (3) |
Ce2—As1v | 3.002 (5) | 2.974 (5) | 3.029 (5) |
Ce2—As1xi | 3.023 (5) | 3.012 (5) | 3.034 (5) |
Ce2—As2v | 3.0237 (13) | 3.0186 (12) | 3.0287 (13) |
Ce2—As2xii | 3.0237 (13) | 3.0186 (12) | 3.0287 (13) |
Ce2—As3ix | 3.107 (4) | 3.065 (5) | 3.151 (5) |
Ce2—As3xiii | 3.134 (4) | 3.080 (5) | 3.188 (5) |
Ce2—As3xiv | 3.134 (4) | 3.080 (5) | 3.188 (5) |
Ce2—As3iii | 3.107 (4) | 3.065 (5) | 3.151 (5) |
Au1—Au1i | 2.8815 (18) | 2.870 (3) | 2.893 (3) |
Au1—Au1iv | 2.9227 (18) | 2.913 (3) | 2.932 (3) |
Au1—Au1xv | 2.901 (2) | 2.889 (2) | 2.914 (2) |
Au1—Au1iii | 2.913 (2) | 2.900 (2) | 2.925 (2) |
Au1—As1xvi | 2.765 (4) | 2.735 (4) | 2.795 (4) |
Au1—As1iv | 2.735 (4) | 2.718 (4) | 2.753 (4) |
Au1—As2xvii | 2.744 (4) | 2.720 (4) | 2.767 (4) |
Au1—As2v | 2.747 (4) | 2.719 (4) | 2.773 (4) |
As3—As3vii | 3.241 (5) | 3.211 (6) | 3.275 (6) |
As3—As3xviii | 2.569 (5) | 2.519 (6) | 2.623 (6) |
As3—As3xv | 2.861 (6) | 2.699 (5) | 3.026 (5) |
As3—As3iii | 2.953 (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, −x2−1/2, x3, x4; (xvi) x1−1, x2, x3, x4; (xvii) x1, x2−1, x3, x4; (xviii) −x1+1, −x2, −x3, −x4. |
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