The incommensurately modulated crystal structure of the mineral daliranite has been determined using 3D electron diffraction data obtained on nanocrystalline domains. Daliranite is orthorhombic with a = 21, b = 4.3, c = 9.5 Å and shows modulation satellites along c. The solution of the average structure in the Pnma space group together with energy-dispersive X-ray spectroscopy data obtained on the same domains indicate a chemical formula of PbHgAs2S5, which has one S fewer than previously reported. The crystal structure of daliranite is built from columns of face-sharing PbS8 bicapped trigonal prisms laterally connected by [2+4]Hg polyhedra and (As3+2S5)4− groups. The excellent quality of the electron diffraction data allows a structural model to be built for the modulated structure in superspace, which shows that the modulation is due to an alternated occupancy of a split As site.
Supporting information
B-IncStrDB reference: 15062EdDLkO
CCDC references: 1917352; 1917353
For both structures, data reduction: PETS 2.0 (Palatinus et al., 2011); program(s) used to solve structure: SIR2014 (Burla et al., 2015); program(s) used to refine structure: Jana2006 (Petricek et al., 2014); molecular graphics: Vesta (Momma & Izumi, 2011).
Crystal data top
As2HgPbS5 | Dx = 5.493 Mg m−3 |
Mr = 717.9 | Electron radiation, λ = 0.0335 Å |
Orthorhombic, Pnma | Cell parameters from 2033 reflections |
a = 21.246 (5) Å | θ = 0.1–1.2° |
b = 4.2897 (9) Å | µ = 0 mm−1 |
c = 9.5257 (12) Å | T = 298 K |
V = 868.2 (3) Å3 | Needle, orange |
Z = 4 | 0.0002 × 0.0001 × 0.0001 mm |
F(000) = 1232 | |
Data collection top
TEM diffractometer | Rint = 0.335 |
Radiation source: LaB6 | θmax = 1.2°, θmin = 0.1° |
10451 measured reflections | h = −20→20 |
562 independent reflections | k = −4→3 |
401 reflections with I > 3σ(I) | l = −8→10 |
Refinement top
Refinement on F | 0 restraints |
R[F2 > 2σ(F2)] = 0.244 | 0 constraints |
wR(F2) = 0.303 | Weighting scheme based on measured s.u.'s w = 1/(σ2(F) + 0.0001F2) |
S = 13.93 | (Δ/σ)max = 0.0002 |
562 reflections | Δρmax = 0.45 e Å−3 |
34 parameters | Δρmin = −0.40 e Å−3 |
Special details top
Experimental. data have been collected by precession assisted 3D electron diffraction |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Pb1 | 0.2886 (7) | 0.25 | 1.3368 (8) | 0.083 (6) | |
Hg1 | 0.4150 (6) | 0.25 | 0.9831 (7) | 0.065 (5) | |
As1 | 0.1286 (13) | 0.356 (3) | 1.1428 (18) | 0.030 (6)* | 0.5 |
As2 | 0.0526 (12) | 0.356 (3) | 0.8089 (16) | 0.019 (6)* | 0.5 |
S1 | 0.2233 (15) | 0.25 | 1.060 (2) | 0.034 (7)* | |
S2 | 0.1437 (15) | 0.25 | 0.690 (2) | 0.036 (7)* | |
S3 | 0.3337 (16) | 0.25 | 0.805 (2) | 0.042 (7)* | |
S4 | 0.4132 (13) | 0.25 | 1.4762 (19) | 0.019 (6)* | |
S5 | 0.4954 (15) | 0.25 | 1.160 (2) | 0.040 (7)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Pb1 | 0.137 (16) | 0.101 (8) | 0.011 (5) | 0 | −0.002332 | 0 |
Hg1 | 0.118 (14) | 0.069 (6) | 0.009 (5) | 0 | 0.001652 | 0 |
Geometric parameters (Å, º) top
Pb1—S1 | 2.982 (17) | | |
| | | |
Pb1—S1—S2 | 177.9 | | |
Crystal data top
As2HgPbS5 | F(000) = 1232 |
Mr = 717.9 | Dx = 5.493 Mg m−3 |
Orthorhombic, Pnma(00γ)0s0† | Electron radiation, λ = 0.0335 Å |
q = 0.262(2)c* | Cell parameters from 10451 reflections |
a = 21.246 (5) Å | θ = 0.1–1.2° |
b = 4.2897 (9) Å | µ = 0 mm−1 |
c = 9.5257 (12) Å | T = 298 K |
V = 868.2 (3) Å3 | Needle, orange |
Z = 4 | 0.0002 × 0.0001 × 0.0001 mm |
† Symmetry operations: (1) x1, x2, x3, x4; (2) −x1+1/2, −x2, x3+1/2, x4+1/2; (3) −x1, x2+1/2, −x3, −x4+1/2; (4) x1+1/2, −x2+1/2, −x3+1/2, −x4; (5) −x1, −x2, −x3, −x4; (6) x1+1/2, x2, −x3+1/2, −x4+1/2; (7) x1, −x2+1/2, x3, x4+1/2; (8) −x1+1/2, x2+1/2, x3+1/2, x4.
|
Data collection top
TEM diffractometer | Rint = 0.335 |
Radiation source: LaB6 | θmax = 1.2°, θmin = 0.1° |
10451 measured reflections | h = −20→20 |
1503 independent reflections | k = −4→3 |
981 reflections with I > 3σ(I) | l = −8→10 |
Refinement top
Refinement on F | 0 restraints |
R[F2 > 2σ(F2)] = 0.272 | 0 constraints |
wR(F2) = 0.310 | Weighting scheme based on measured s.u.'s w = 1/(σ2(F) + 0.0001F2) |
S = 10.70 | (Δ/σ)max = 0.001 |
1503 reflections | Δρmax = 0.45 e Å−3 |
38 parameters | Δρmin = −0.40 e Å−3 |
Special details top
Experimental. data have been collected by precession assisted 3D electron diffraction |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Pb1 | 0.2885 (5) | 0.25 | 1.3367 (5) | 0.061 (4) | |
Hg1 | 0.4149 (5) | 0.25 | 0.9835 (5) | 0.063 (4) | |
As1 | 0.1285 (8) | 0.371 (2) | 1.1430 (11) | 0.031 (3)* | 0.5 |
As2 | 0.0517 (7) | 0.365 (2) | 0.8082 (10) | 0.027 (3)* | 0.5 |
S1 | 0.2236 (10) | 0.25 | 1.0596 (15) | 0.027 (4)* | |
S2 | 0.1430 (9) | 0.25 | 0.6898 (14) | 0.019 (4)* | |
S3 | 0.3344 (11) | 0.25 | 0.8066 (15) | 0.026 (4)* | |
S4 | 0.4134 (8) | 0.25 | 1.4756 (12) | 0.007 (4)* | |
S5 | 0.4962 (10) | 0.25 | 1.1610 (15) | 0.030 (5)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Pb1 | 0.132 (11) | 0.033 (4) | 0.018 (3) | 0 | −0.003 (4) | 0 |
Hg1 | 0.122 (10) | 0.060 (4) | 0.006 (3) | 0 | 0.002 (3) | 0 |
Bond lengths (Å) top | Average | Minimum | Maximum |
Pb1—S1 | 2.982 (17) | 2.979 (17) | 2.986 (17) |
Pb1—S1i | 3.031 (11) | 2.912 (11) | 3.151 (11) |
Pb1—S1ii | 3.029 (11) | 2.912 (11) | 3.151 (11) |
Pb1—S2i | 2.948 (13) | 2.808 (13) | 3.087 (13) |
Pb1—S2ii | 2.945 (13) | 2.808 (13) | 3.087 (13) |
Pb1—S3i | 3.403 (19) | 3.13 (2) | 3.69 (2) |
Pb1—S3ii | 3.398 (19) | 3.13 (2) | 3.69 (2) |
Pb1—S4 | 2.975 (19) | 2.963 (19) | 2.985 (19) |
Hg1—S2i | 3.159 (12) | 3.114 (12) | 3.205 (12) |
Hg1—S2ii | 3.159 (12) | 3.114 (12) | 3.205 (12) |
Hg1—S3 | 2.40 (2) | 2.40 (2) | 2.40 (2) |
Hg1—S5 | 2.43 (2) | 2.42 (2) | 2.45 (2) |
Hg1—S5iii | 3.184 (16) | 2.880 (17) | 3.501 (17) |
Hg1—S5iv | 3.179 (16) | 2.880 (17) | 3.501 (17) |
As1—S1 | 2.20 (3) | 2.19 (3) | 2.26 (3) |
As1—S3i | 3.287 (13) | 3.056 (14) | 3.397 (14) |
As1—S3ii | 2.308 (16) | 2.224 (17) | 2.495 (17) |
As1—S4v | 3.212 (13) | 3.141 (13) | 3.316 (13) |
As1—S4vi | 2.460 (15) | 2.377 (15) | 2.518 (15) |
As1—S5vii | 3.41 (2) | 3.39 (2) | 3.44 (2) |
As2—S2 | 2.28 (2) | 2.26 (2) | 2.32 (2) |
As2—S4v | 3.155 (12) | 3.080 (12) | 3.259 (12) |
As2—S4vi | 2.426 (14) | 2.342 (14) | 2.489 (14) |
As2—S5v | 3.239 (14) | 3.083 (14) | 3.309 (14) |
As2—S5vi | 2.328 (17) | 2.272 (17) | 2.455 (17) |
S1—S3 | 3.37 (3) | 3.37 (3) | 3.38 (3) |
S1—S3i | 3.423 (18) | 3.164 (19) | 3.695 (19) |
S1—S3ii | 3.419 (18) | 3.164 (19) | 3.695 (19) |
S2—S5v | 3.67 (2) | 3.47 (3) | 3.88 (3) |
S2—S5vi | 3.67 (2) | 3.47 (3) | 3.88 (3) |
S4—S5 | 3.48 (2) | 3.48 (2) | 3.48 (2) |
Symmetry codes: (i) −x1+1/2, −x2, x3+1/2, x4+1/2; (ii) −x1+1/2, −x2+1, x3+1/2, x4+1/2; (iii) −x1+1, x2−1/2, −x3+2, −x4+1/2; (iv) −x1+1, x2+1/2, −x3+2, −x4+1/2; (v) −x1+1/2, −x2, x3−1/2, x4+1/2; (vi) −x1+1/2, −x2+1, x3−1/2, x4+1/2; (vii) x1−1/2, −x2+1/2, −x3+5/2, −x4. |