inorganic compounds
Wulfenite [lead(II) molybdate(VI)] is known as a scheelite structure in the I41/a space group. The structure of the unusual `hemimorphic' wulfenite crystals from the Mezica mine was refined in the noncentrosymmetric space group I using a Pb/Mo exchange disorder model with the approximate composition Pb0.94Mo0.06[MoO4]. Pb atoms in the 2b positions are substituted by Mo at about 12%. The crystal is shown to be twinned by inversion. Hemimorphism may result from the short-range chemical ordering of the metal atoms at the 2b positions.
Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270111015769/ku3043sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270111015769/ku3043Isup2.hkl |
Computing details top
Data collection: CrystalClear (Rigaku, 2008); cell refinement: CrystalClear (Rigaku, 2008); data reduction: CrystalClear (Rigaku, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).
lead(II) molybdate(VI) top
Crystal data top
Pb0.94Mo0.06[MoO4] | Dx = 6.671 Mg m−3 |
Mr = 360.42 | Mo Kα radiation, λ = 0.71070 Å |
Tetragonal, I4 | Cell parameters from 2580 reflections |
Hall symbol: I -4 | θ = 3.4–45.3° |
a = 5.442 (1) Å | µ = 47.59 mm−1 |
c = 12.1177 (14) Å | T = 294 K |
V = 358.87 (5) Å3 | Chip, yellow |
Z = 4 | 0.10 × 0.10 × 0.05 mm |
F(000) = 614 |
Data collection top
Rigaku R-AXIS RAPID diffractometer | 335 independent reflections |
Radiation source: normal-focus sealed tube | 333 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.120 |
Detector resolution: 10.0000 pixels mm-1 | θmax = 25.3°, θmin = 3.4° |
dtprofit.ref scans | h = −6→6 |
Absorption correction: numerical (NUMABS; Higashi, 2002) | k = −6→6 |
Tmin = 0.064, Tmax = 0.336 | l = −14→14 |
6322 measured reflections |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | w = 1/[σ2(Fo2) + (0.0244P)2 + 3.452P] where P = (Fo2 + 2Fc2)/3 |
R[F2 > 2σ(F2)] = 0.025 | (Δ/σ)max = 0.049 |
wR(F2) = 0.061 | Δρmax = 0.71 e Å−3 |
S = 1.16 | Δρmin = −0.86 e Å−3 |
335 reflections | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
30 parameters | Extinction coefficient: 0.0140 (8) |
0 restraints | Absolute structure: Flack (1983), ???? Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.50 (6) |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Pb1 | 0.5000 | 0.0000 | 0.2500 | 0.0213 (13) | |
Mo2 | 0.0000 | 0.0000 | 0.0000 | 0.022 (4) | |
Pb3 | 0.5000 | 0.5000 | 0.0000 | 0.025 (2) | 0.881 (8) |
Mo3 | 0.5000 | 0.5000 | 0.0000 | 0.025 (2) | 0.119 (8) |
Mo1 | 0.0000 | 0.5000 | 0.2500 | 0.018 (3) | |
O1 | 0.2344 (13) | −0.1372 (14) | 0.0806 (6) | 0.0302 (17) | |
O2 | 0.2338 (14) | 0.3648 (14) | 0.1697 (6) | 0.0307 (17) |
Atomic displacement parameters (Å2) top
U11 | U22 | U33 | U12 | U13 | U23 | |
Pb1 | 0.021 (2) | 0.021 (2) | 0.022 (2) | 0.000 | 0.000 | 0.000 |
Mo2 | 0.020 (6) | 0.020 (6) | 0.025 (7) | 0.000 | 0.000 | 0.000 |
Pb3 | 0.023 (3) | 0.023 (3) | 0.027 (4) | 0.000 | 0.000 | 0.000 |
Mo3 | 0.023 (3) | 0.023 (3) | 0.027 (4) | 0.000 | 0.000 | 0.000 |
Mo1 | 0.016 (5) | 0.016 (5) | 0.021 (6) | 0.000 | 0.000 | 0.000 |
O1 | 0.033 (5) | 0.030 (4) | 0.028 (4) | 0.002 (3) | −0.005 (3) | 0.004 (3) |
O2 | 0.030 (5) | 0.028 (4) | 0.034 (4) | 0.001 (3) | −0.003 (3) | 0.011 (4) |
Geometric parameters (Å, º) top
Pb1—O1 | 2.619 (7) | Pb3—O2viii | 2.620 (7) |
Pb1—O1i | 2.619 (7) | Pb3—O2ix | 2.620 (7) |
Pb1—O1ii | 2.619 (7) | Pb3—O2 | 2.620 (7) |
Pb1—O1iii | 2.619 (7) | Pb3—O1v | 2.635 (8) |
Pb1—O2i | 2.643 (8) | Pb3—O1x | 2.635 (8) |
Pb1—O2ii | 2.643 (8) | Pb3—O1xi | 2.635 (8) |
Pb1—O2iii | 2.643 (8) | Pb3—O1iii | 2.635 (8) |
Pb1—O2 | 2.643 (8) | Mo1—O2xii | 1.763 (8) |
Mo2—O1iv | 1.772 (7) | Mo1—O2xiii | 1.763 (8) |
Mo2—O1 | 1.772 (7) | Mo1—O2xiv | 1.763 (8) |
Mo2—O1v | 1.772 (7) | Mo1—O2 | 1.763 (8) |
Mo2—O1vi | 1.772 (7) | O1—Pb3xv | 2.635 (8) |
Pb3—O2vii | 2.620 (7) | ||
O1—Pb1—O1i | 127.9 (2) | O2vii—Pb3—O2 | 76.6 (3) |
O1—Pb1—O1ii | 127.9 (2) | O2viii—Pb3—O2 | 128.0 (2) |
O1i—Pb1—O1ii | 76.8 (3) | O2ix—Pb3—O2 | 128.0 (2) |
O1—Pb1—O1iii | 76.8 (3) | O2vii—Pb3—O1v | 149.2 (2) |
O1i—Pb1—O1iii | 127.9 (2) | O2viii—Pb3—O1v | 67.4 (3) |
O1ii—Pb1—O1iii | 127.9 (2) | O2ix—Pb3—O1v | 78.6 (2) |
O1—Pb1—O2i | 149.2 (2) | O2—Pb3—O1v | 73.9 (3) |
O1i—Pb1—O2i | 67.9 (3) | O2vii—Pb3—O1x | 73.9 (3) |
O1ii—Pb1—O2i | 78.4 (2) | O2viii—Pb3—O1x | 78.6 (2) |
O1iii—Pb1—O2i | 73.6 (3) | O2ix—Pb3—O1x | 67.4 (3) |
O1—Pb1—O2ii | 73.6 (3) | O2—Pb3—O1x | 149.2 (2) |
O1i—Pb1—O2ii | 78.4 (2) | O1v—Pb3—O1x | 136.5 (3) |
O1ii—Pb1—O2ii | 67.9 (3) | O2vii—Pb3—O1xi | 78.6 (2) |
O1iii—Pb1—O2ii | 149.2 (2) | O2viii—Pb3—O1xi | 149.2 (2) |
O2i—Pb1—O2ii | 136.8 (3) | O2ix—Pb3—O1xi | 73.9 (3) |
O1—Pb1—O2iii | 78.4 (2) | O2—Pb3—O1xi | 67.4 (3) |
O1i—Pb1—O2iii | 149.2 (2) | O1v—Pb3—O1xi | 97.90 (11) |
O1ii—Pb1—O2iii | 73.6 (3) | O1x—Pb3—O1xi | 97.90 (11) |
O1iii—Pb1—O2iii | 67.9 (3) | O2vii—Pb3—O1iii | 67.4 (3) |
O2i—Pb1—O2iii | 97.79 (12) | O2viii—Pb3—O1iii | 73.9 (3) |
O2ii—Pb1—O2iii | 97.79 (12) | O2ix—Pb3—O1iii | 149.2 (2) |
O1—Pb1—O2 | 67.9 (3) | O2—Pb3—O1iii | 78.6 (2) |
O1i—Pb1—O2 | 73.6 (3) | O1v—Pb3—O1iii | 97.90 (11) |
O1ii—Pb1—O2 | 149.2 (2) | O1x—Pb3—O1iii | 97.90 (11) |
O1iii—Pb1—O2 | 78.4 (2) | O1xi—Pb3—O1iii | 136.5 (3) |
O2i—Pb1—O2 | 97.79 (12) | O2xii—Mo1—O2xiii | 107.8 (2) |
O2ii—Pb1—O2 | 97.79 (12) | O2xii—Mo1—O2xiv | 113.0 (5) |
O2iii—Pb1—O2 | 136.8 (3) | O2xiii—Mo1—O2xiv | 107.8 (2) |
O1iv—Mo2—O1 | 107.7 (2) | O2xii—Mo1—O2 | 107.8 (2) |
O1iv—Mo2—O1v | 113.1 (5) | O2xiii—Mo1—O2 | 113.0 (5) |
O1—Mo2—O1v | 107.7 (2) | O2xiv—Mo1—O2 | 107.8 (2) |
O1iv—Mo2—O1vi | 107.7 (2) | Mo2—O1—Pb1 | 135.2 (4) |
O1—Mo2—O1vi | 113.1 (5) | Mo2—O1—Pb3xv | 120.4 (4) |
O1v—Mo2—O1vi | 107.7 (2) | Pb1—O1—Pb3xv | 101.6 (2) |
O2vii—Pb3—O2viii | 128.0 (2) | Mo1—O2—Pb3 | 135.6 (4) |
O2vii—Pb3—O2ix | 128.0 (2) | Mo1—O2—Pb1 | 120.4 (3) |
O2viii—Pb3—O2ix | 76.6 (3) | Pb3—O2—Pb1 | 101.4 (3) |
Symmetry codes: (i) y+1/2, −x+1/2, −z+1/2; (ii) −y+1/2, x−1/2, −z+1/2; (iii) −x+1, −y, z; (iv) y, −x, −z; (v) −y, x, −z; (vi) −x, −y, z; (vii) −x+1, −y+1, z; (viii) −y+1, x, −z; (ix) y, −x+1, −z; (x) y+1, −x+1, −z; (xi) x, y+1, z; (xii) −y+1/2, x+1/2, −z+1/2; (xiii) −x, −y+1, z; (xiv) y−1/2, −x+1/2, −z+1/2; (xv) x, y−1, z. |
Fractional atomic coordinates and isotropic or equivalent isotropic
displacement parameters (Å2) top
Wyckoff position | x | y | z | Uiso*/Ueq | Occ. (<1) | |
Pb1 | 2d | 0.5000 | 0.0000 | 0.2500 | 0.0213 (13) | |
Mo1 | 2c | 0.0000 | 0.5000 | 0.2500 | 0.018 (3) | |
Mo2 | 2a | 0.0000 | 0.0000 | 0.0000 | 0.022 (4) | |
Pb3 | 2b | 0.5000 | 0.5000 | 0.0000 | 0.025 (2) | 0.881 (8) |
Mo3 | 2b | 0.5000 | 0.5000 | 0.0000 | 0.025 (2) | 0.119 (8) |
O1 | 8g | 0.2344 (13) | -0.1372 (14) | 0.0806 (6) | 0.0302 (17) | |
O2 | 8g | 0.2338 (14) | 0.3648 (14) | 0.1697 (6) | 0.0307 (17) |
Pb—O and Mo—O bond lengths (Å) top
This work | Lugli <it> et al.</it> (1999) | |
Pb1—O1 | 2.619 (7) | 2.611 (3) |
Pb1—O2 | 2.643 (8) | 2.636 (3) |
Mo2—O1 | 1.772 (7) | 1.769 (3) |
Pb3—O2 | 2.620 (7) | 2.611 (3) |
Pb3—O1 | 2.635 (8) | 2.636 (3) |
Mo1—O2 | 1.763 (8) | 1.769 (3) |
Symmetry codes: (i) y + 1/2, -x + 1/2, -z + 1/2; (ii) -y + 1/2, x - 1/2, -z + 1/2; (iii) -x + 1, -y, z; (iv) y, -x, -z; (v) -y, x, -z; (vi) -x, -y, z; (vii) -x + 1, -y + 1, z; (viii) -y + 1, x, -z; (ix) y, -x + 1, -z; (x) y + 1, -x + 1, -z; (xi) x, y + 1, z; (xii) -y + 1/2, x + 1/2, -z + 1/2; (xiii) -x, -y + 1, z; (xiv) y - 1/2, -x + 1/2, -z + 1/2; (xv) x, y - 1, z. |