research papers
Monophosphate tungsten bronze with pentagonal tunnels (PO2)4(WO3)2m are low-dimensional materials with charge density wave (CDW)-type electron instabilities. Two forms of the structure can thus be expected for all the members of the series: a low-temperature form (LT) corresponding to the CDW state and a high-temperature form (HT) corresponding to a normal metallic state. The HT form is described here for m = 9 and compared with that of the m = 5 and m = 7 counterparts. It is shown that a systematic twin phenomenon must be taken into account for HT members because of two possible configurations of the tilting mode of WO6 octahedra. The structure is also compared with that of m = 10, which exhibits the modulated CDW–LT form at room temperature. Owing to two possible polarization directions of the segments built of m WO6 octahedra, a twin phenomenon is also encountered in the LT forms. A review of all the structures known at present (m = 2, 4, 5, 6, 7, 8, 9, 10, 12) leads us to propose a structural law based on the building mode of WO6 octahedra in WO3-type slabs to explain the symmetry changes observed between even and odd members of the series.
Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768199016195/lc0016sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108768199016195/lc0016sup2.hkl |
Computing details top
Data collection: CAD4 (Enraf Nonius, 1980); cell refinement: SET4 (Enraf Nonius, 1989).
(LC0016) top
Crystal data top
O62P4W18 | Z = 1 |
Mr = 4425.1 | F(000) = 1888 |
Triclinic, P1 | Dx = 6.477 Mg m−3 |
a = 5.2945 (9) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 6.542 (2) Å | Cell parameters from 17 reflections |
c = 32.744 (5) Å | θ = 5–43° |
α = 90.00 (2)° | µ = 45.71 mm−1 |
β = 90.20 (2)° | T = 293 K |
γ = 89.78 (2)° | Platelet, dark blue |
V = 1134.2 (4) Å3 | 158 × 144 × 4 mm |
Data collection top
Enraf Nonius CAD4 diffractometer | θmax = 45°, θmin = 2° |
type 2 scans | h = 0→10 |
Absorption correction: gaussian ? | k = −12→12 |
Tmin = 0.148, Tmax = 0.833 | l = −64→64 |
20410 measured reflections | 3 standard reflections every 60 min |
20041 independent reflections | intensity decay: <4% |
4661 reflections with I > 3σ(I) |
Refinement top
Refinement on F | 200 parameters |
R[F2 > 2σ(F2)] = 0.057 | Weighting scheme based on measured s.u.'s w = 1/σ2(F) |
wR(F2) = 0.047 | (Δ/σ)max = 0.001 |
S = 2.79 | Δρmax = 1.44 e Å−3 |
4661 reflections | Δρmin = −1.34 e Å−3 |
Crystal data top
O62P4W18 | γ = 89.78 (2)° |
Mr = 4425.1 | V = 1134.2 (4) Å3 |
Triclinic, P1 | Z = 1 |
a = 5.2945 (9) Å | Mo Kα radiation |
b = 6.542 (2) Å | µ = 45.71 mm−1 |
c = 32.744 (5) Å | T = 293 K |
α = 90.00 (2)° | 158 × 144 × 4 mm |
β = 90.20 (2)° |
Data collection top
Enraf Nonius CAD4 diffractometer | 20041 independent reflections |
Absorption correction: gaussian ? | 4661 reflections with I > 3σ(I) |
Tmin = 0.148, Tmax = 0.833 | 3 standard reflections every 60 min |
20410 measured reflections | intensity decay: <4% |
Refinement top
R[F2 > 2σ(F2)] = 0.057 | 200 parameters |
wR(F2) = 0.047 | Δρmax = 1.44 e Å−3 |
S = 2.79 | Δρmin = −1.34 e Å−3 |
4661 reflections |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
x | y | z | Uiso*/Ueq | ||
W1a | 0.0038 (2) | 0.3258 (2) | 0.81485 (3) | 0.0084 (3) | |
W2a | 0.4992 (2) | −0.0139 (2) | 0.86117 (4) | 0.0092 (3) | |
W3a | 0.0040 (2) | −0.3425 (2) | 0.90852 (4) | 0.0107 (3) | |
W4a | 0.4996 (2) | −0.3287 (2) | 0.04583 (4) | 0.0110 (4) | |
W5a | 0.0 | 0.0 | 0.0 | 0.0120 (5) | |
W1b | 0.5061 (2) | 0.8257 (1) | 0.68501 (4) | 0.0071 (3) | |
W2b | 0.0083 (2) | 0.4876 (2) | 0.63874 (4) | 0.0097 (3) | |
W3b | 0.5021 (2) | 0.1572 (2) | 0.59152 (4) | 0.0104 (3) | |
W4b | 0.0023 (2) | 0.8289 (2) | 0.54569 (4) | 0.0115 (4) | |
W5b | 1.5 | 0.5 | 0.5 | 0.0115 (4) | |
Pa | 0.499 (1) | −0.3636 (8) | 0.7832 (2) | 0.0008 (9) | |
Pb | 0.011 (1) | 0.1369 (9) | 0.7173 (2) | 0.004 (1) | |
O1a | 0.239 (3) | 0.531 (2) | 0.7873 (5) | 0.018 (4) | |
O2a | 0.732 | −0.489 | 0.7927 | 0.013 | |
O3a | −0.013 | 0.208 | 0.7596 | 0.013 | |
O4a | 0.998 (4) | −0.497 (3) | 0.8578 (7) | 0.021 (5) | |
O5a | 0.783 (3) | 0.142 (2) | 0.8367 (5) | 0.008 (3) | |
O6a | 0.276 (4) | 0.175 (3) | 0.8321 (6) | 0.023 (4) | |
O7a | 0.511 (4) | −0.169 (3) | 0.8088 (7) | 0.019 (5) | |
O8a | 0.501 (3) | 0.163 (2) | 0.9041 (6) | 0.008 (4) | |
O9a | 0.721 (3) | −0.192 (2) | 0.8836 (5) | 0.008 (3) | |
O10a | 0.214 (3) | −0.147 (2) | 0.8797 (5) | 0.016 (3) | |
O11a | 0.998 (3) | −0.166 (3) | 0.9519 (6) | 0.010 (4) | |
O12a | 0.789 (3) | −0.533 (2) | 0.9330 (4) | 0.007 (2) | |
O13a | 0.287 (3) | −0.474 (2) | 0.9253 (4) | 0.008 (3) | |
O14a | 0.5 | −0.5 | 0.0 | 0.021 (7) | |
O15a | 0.215 (3) | 0.192 (2) | 0.9734 (5) | 0.008 (3) | |
O16a | 0.287 (3) | −0.137 (2) | 0.0197 (5) | 0.007 (3) | |
O1b | 0.275 (3) | 0.028 (2) | 0.7126 (5) | 0.015 (3) | |
O2b | 0.809 | 0.982 | 0.7074 | 0.013 | |
O3b | 0.498 | 0.690 | 0.7386 | 0.013 | |
O4b | 0.518 (3) | 0.991 (2) | 0.6403 (6) | 0.010 (4) | |
O5b | 0.233 (3) | 0.679 (2) | 0.6714 (4) | 0.007 (3) | |
O6b | 0.733 (3) | 0.641 (2) | 0.6650 (5) | 0.010 (3) | |
O7b | 0.995 (4) | 0.323 (3) | 0.6897 (7) | 0.018 (5) | |
O8b | 0.005 (3) | 0.662 (3) | 0.5957 (7) | 0.011 (5) | |
O9b | 0.790 (3) | 0.305 (2) | 0.6159 (5) | 0.013 (3) | |
O10b | 0.291 (3) | 0.351 (2) | 0.6236 (4) | 0.006 (2) | |
O11b | 0.506 (3) | 0.329 (3) | 0.5470 (6) | 0.011 (5) | |
O12b | 0.718 (2) | 0.973 (2) | 0.5682 (4) | 0.005 (3) | |
O13b | 0.214 (2) | 0.022 (2) | 0.5749 (4) | 0.003 (2) | |
O14b | 0.0 | 0.0 | 0.5 | 0.014 (6) | |
O15b | 0.787 (3) | 0.637 (2) | 0.5219 (5) | 0.013 (3) | |
O16b | 0.286 (3) | 0.688 (2) | 0.5288 (4) | 0.006 (3) |
Atomic displacement parameters (Å2) top
U11 | U22 | U33 | U12 | U13 | U23 | |
W1a | 0.0110 (5) | 0.0092 (5) | 0.0051 (5) | 0.0033 (4) | −0.0002 (4) | −0.0019 (4) |
W2a | 0.0141 (5) | 0.0068 (4) | 0.0066 (4) | 0.0016 (4) | −0.0017 (4) | −0.0025 (4) |
W3a | 0.0128 (6) | 0.0100 (5) | 0.0093 (6) | 0.0042 (5) | −0.0037 (5) | −0.0040 (4) |
W4a | 0.0135 (7) | 0.0106 (5) | 0.0088 (7) | 0.0030 (5) | −0.0028 (5) | −0.0046 (5) |
W5a | 0.0126 (8) | 0.0130 (7) | 0.0103 (8) | 0.0040 (6) | −0.0028 (7) | −0.0055 (7) |
W1b | 0.0079 (5) | 0.0067 (4) | 0.0067 (5) | 0.0004 (4) | 0.0029 (4) | 0.0004 (4) |
W2b | 0.0111 (5) | 0.0082 (5) | 0.0096 (5) | 0.0035 (4) | 0.0037 (4) | 0.0044 (4) |
W3b | 0.0144 (6) | 0.0093 (5) | 0.0074 (6) | 0.0030 (5) | 0.0041 (5) | 0.0030 (4) |
W4b | 0.0137 (7) | 0.0124 (6) | 0.0084 (7) | 0.0064 (5) | 0.0048 (5) | 0.0053 (4) |
W5b | 0.0165 (9) | 0.0135 (8) | 0.0045 (7) | 0.0079 (7) | 0.0040 (6) | 0.0058 (6) |
Bond lengths (Å) top
W1a—O1a | 2.05 (1) | W1b—O5bii | 1.79 (1) |
W1a—O2ai | 2.01 (2) | W1b—O6b | 1.82 (1) |
W1a—O3a | 1.97 (3) | W2b—O5b | 2.03 (1) |
W1a—O4ai | 1.82 (2) | W2b—O6b | 1.97 (2) |
W1a—O5aii | 1.83 (1) | W2b—O7b | 1.99 (2) |
W1a—O6a | 1.83 (2) | W2b—O8b | 1.81 (2) |
W2a—O5a | 1.99 (2) | W2b—O9bvii | 1.82 (1) |
W2a—O6a | 1.95 (2) | W2b—O10bviii | 1.81 (2) |
W2a—O7a | 1.99 (2) | W3b—O4b | 1.93 (2) |
W2a—O8a | 1.82 (2) | W3b—O9b | 1.97 (2) |
W2a—O9a | 1.81 (1) | W3b—O10b | 1.99 (1) |
W2a—O10aii | 1.85 (2) | W3b—O11bi | 1.84 (2) |
W3a—O4a | 1.94 (2) | W3b—O12b | 1.83 (1) |
W3a—O9a | 1.96 (2) | W3b—O13b | 1.85 (1) |
W3a—O10a | 1.94 (1) | W4b—O8b | 1.97 (2) |
W3a—O11a | 1.83 (2) | W4b—O12b | 1.92 (1) |
W3a—O12a | 1.87 (1) | W4b—O13bix | 1.94 (1) |
W3a—O13a | 1.81 (2) | W4b—O14b | 1.868 (1) |
W4a—O8aiii | 1.97 (2) | W4b—O15bii | 1.87 (1) |
W4a—O12aiv | 1.91 (1) | W4b—O16b | 1.85 (1) |
W4a—O13av | 1.95 (1) | W5b—O11b | 1.90 (2) |
W4a—O14a | 1.873 (1) | W5b—O11bx | 1.90 (2) |
W4a—O15avi | 1.87 (2) | W5b—O15b | 1.91 (2) |
W4a—O16aii | 1.89 (1) | W5b—O15bx | 1.91 (2) |
W5a—O11a | 1.91 (2) | W5b—O16b | 1.92 (1) |
W5a—O11avi | 1.91 (2) | W5b—O16bx | 1.92 (1) |
W5a—O15a | 1.91 (1) | Pa—O1avii | 1.55 (2) |
W5a—O15avi | 1.91 (1) | Pa—O2a | 1.51 (2) |
W5a—O16a | 1.87 (2) | Pa—O7a | 1.53 (2) |
W5a—O16avi | 1.87 (2) | Pa—O3bvii | 1.50 (1) |
W1b—O1bi | 2.02 (1) | Pb—O3aix | 1.47 (3) |
W1b—O2b | 2.04 (2) | Pb—O1b | 1.57 (2) |
W1b—O3b | 1.97 (1) | Pb—O2bvii | 1.51 (2) |
W1b—O4b | 1.82 (2) | Pb—O7b | 1.52 (2) |
Symmetry codes: (i) x−1, y+1, z; (ii) x−1, y, z; (iii) −x+1, −y, −z+2; (iv) −x+1, −y−1, −z+2; (v) −x+2, −y−1, −z+2; (vi) −x+2, −y, −z+2; (vii) x, y−1, z; (viii) x+1, y−1, z; (ix) x+1, y, z; (x) −x+3, −y+1, −z+1. |
Experimental details
Crystal data | |
Chemical formula | O62P4W18 |
Mr | 4425.1 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 5.2945 (9), 6.542 (2), 32.744 (5) |
α, β, γ (°) | 90.00 (2), 90.20 (2), 89.78 (2) |
V (Å3) | 1134.2 (4) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 45.71 |
Crystal size (mm) | 158 × 144 × 4 |
Data collection | |
Diffractometer | Enraf Nonius CAD4 diffractometer |
Absorption correction | Gaussian |
Tmin, Tmax | 0.148, 0.833 |
No. of measured, independent and observed [I > 3σ(I)] reflections | 20410, 20041, 4661 |
Rint | ? |
(sin θ/λ)max (Å−1) | 0.995 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.057, 0.047, 2.79 |
No. of reflections | 4661 |
No. of parameters | 200 |
No. of restraints | ? |
Δρmax, Δρmin (e Å−3) | 1.44, −1.34 |
Computer programs: CAD4 (Enraf Nonius, 1980), SET4 (Enraf Nonius, 1989).