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The crystal structure of the third polymorph of the Cu7PSe6 argyrodite compound, α-Cu7PSe6, heptacopper phosphorus hexaselenide, is determined by means of single-crystal diffraction from twinned crystals and X-ray powder diffraction, with the help of extensive NMR measurements. In the low-temperature form, i.e. below the last phase transition, α-Cu7PSe6 crystallizes in orthorhombic symmetry, space group Pna21, with a = 14.3179 (4), b = 7.1112 (2), c = 10.1023 (3) Å, V = 1028.590 (9) Å3 (deduced from powder data, T = 173 K) and Z = 4. Taking into account a twinning by reticular merohedry, the refinement of the α-Cu7PSe6 structure leads to the residual factors R = 0.0466 and wR = 0.0486 for 127 parameters and 3714 observed, independent reflections (single-crystal data, T = 173 K). A full localization of the Cu+d10 element is reached with one twofold-, one threefold- and five fourfold-coordinated Cu atoms. The observation of two phase transitions for Cu7PSe6, to be compared with only one for Ag7PSe6, is attributed to the d10 element stability in a low coordination environment, copper being less prone to lower coordination sites than silver, especially at low temperature.
Supporting information
Crystal data top
Cu7PSe6 | V = 1028.59 (5) Å3 |
Mr = 949.6 | Z = 4 |
Orthorhombic, Pna21 | F(000) = 1688 |
Hall symbol: P 2c -2n | Dx = 6.117 Mg m−3 |
a = 14.3179 (4) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 7.1112 (2) Å | µ = 352.9 mm−1 |
c = 10.1023 (3) Å | × × mm |
Data collection top
STOE IPDS diffractometer | 3714 reflections with 3 |
Absorption correction: spherical ? | h = ?→? |
Tmin = 0.053, Tmax = 0.145 | k = ?→? |
29369 independent reflections | l = ?→? |
Refinement top
Refinement on F | Weighting scheme based on measured s.u.'s w = 1/(σ2(F) + 0.0004F2) |
R[F2 > 2σ(F2)] = 0.047 | (Δ/σ)max = 0.004 |
wR(F2) = 0.080 | Δρmax = 2.30 e Å−3 |
S = 1.06 | Δρmin = −2.02 e Å−3 |
29369 reflections | Extinction correction: B-C type 1 Lorentzian isotropic |
127 parameters | Extinction coefficient: 0.018565 |
Crystal data top
Cu7PSe6 | V = 1028.59 (5) Å3 |
Mr = 949.6 | Z = 4 |
Orthorhombic, Pna21 | Mo Kα radiation |
a = 14.3179 (4) Å | µ = 352.9 mm−1 |
b = 7.1112 (2) Å | × × mm |
c = 10.1023 (3) Å | |
Data collection top
STOE IPDS diffractometer | 29369 independent reflections |
Absorption correction: spherical ? | 3714 reflections with 3 |
Tmin = 0.053, Tmax = 0.145 | |
Refinement top
R[F2 > 2σ(F2)] = 0.047 | 127 parameters |
wR(F2) = 0.080 | Δρmax = 2.30 e Å−3 |
S = 1.06 | Δρmin = −2.02 e Å−3 |
29369 reflections | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
P | 0.1239 (3) | 0.7531 (6) | 0.2500 (5) | 0.0027 (4) | |
Se1a | 0.0023 (2) | 0.7567 (3) | 0.1179 (5) | 0.0059 (6) | |
Se1b | 0.2511 (2) | 0.2514 (2) | 0.6242 (5) | 0.0060 (6) | |
Se1c | 0.3787 (1) | 0.5038 (3) | 0.8764 (5) | 0.0067 (6) | |
Se1d | −0.1194 (1) | 0.5047 (3) | 0.8734 (5) | 0.0058 (6) | |
Se2 | 0.1253 (1) | 0.7180 (3) | 0.7351 (5) | 0.0075 (6) | |
Se3 | 0.3847 (1) | 0.7398 (3) | 0.5057 (5) | 0.0089 (7) | |
Cu1a | 0.2375 (2) | 0.4640 (4) | 0.9976 (6) | 0.0224 (9) | |
Cu1b | 0.7709 (2) | 0.4158 (4) | 0.0472 (5) | 0.0173 (8) | |
Cu2 | 0.2936 (2) | 0.7675 (4) | 0.7451 (6) | 0.0237 (8) | |
Cu3a | 0.9671 (2) | 0.0921 (4) | 0.0879 (6) | 0.0240 (9) | |
Cu3b | 0.5513 (2) | 0.9364 (4) | 0.9281 (5) | 0.0191 (9) | |
Cu4a | 0.8575 (3) | 0.0214 (6) | 0.3652 (7) | 0.0523 (14) | |
Cu4b | 0.3765 (2) | 0.8298 (5) | 0.2702 (5) | 0.0308 (10) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Se1a | 0.0065 (9) | 0.007 (1) | 0.004 (1) | 0.0010 (7) | 0.0010 (7) | −0.0001 (8) |
Se1b | 0.0061 (9) | 0.007 (1) | 0.005 (1) | −0.0010 (8) | 0.0041 (7) | 0.0009 (9) |
Se1c | 0.0085 (9) | 0.006 (1) | 0.006 (1) | 0.0014 (9) | 0.0015 (9) | 0.0024 (7) |
Se1d | 0.0069 (9) | 0.006 (1) | 0.005 (1) | 0.0022 (9) | −0.0002 (9) | 0.0030 (7) |
Se2 | 0.0074 (9) | 0.0057 (9) | 0.009 (1) | −0.0009 (8) | −0.001 (1) | −0.0016 (7) |
Se3 | 0.0061 | 0.012 (1) | 0.009 (1) | 0.0008 (8) | 0.0012 (8) | 0.0000 (9) |
Cu1a | 0.017 (1) | 0.016 (1) | 0.034 (2) | −0.008 (1) | −0.012 (1) | 0.010 (1) |
Cu1b | 0.016 (1) | 0.020 (1) | 0.016 (1) | −0.003 (1) | −0.008 (1) | 0.004 (1) |
Cu2 | 0.013 (1) | 0.024 (2) | 0.034 (2) | −0.006 (1) | 0.010 (1) | 0.004 (2) |
Cu3a | 0.025 (2) | 0.019 (2) | 0.028 (2) | 0.003 (1) | 0.000 (1) | −0.004 (1) |
Cu3b | 0.021 (1) | 0.024 (2) | 0.013 (1) | 0.000 (1) | 0.004 (1) | 0.001 (1) |
Cu4a | 0.048 (2) | 0.044 (2) | 0.065 (3) | 0.004 (2) | −0.004 (2) | −0.040 (2) |
Cu4b | 0.007 (1) | 0.072 (2) | 0.013 (1) | 0.002 (2) | 0.002 (1) | 0.011 (1) |
Bond lengths (Å) top
P—Se1a | 2.194 (5) | Cu2—Se3 | 2.755 (7) |
P—Se1ci | 2.195 (5) | Cu3a—Se2vi | 2.405 (6) |
P—Se1bi | 2.193 (5) | Cu3a—Se1aviii | 2.457 (4) |
P—Se1dii | 2.218 (5) | Cu3a—Se3ix | 2.509 (4) |
Cu1a—Se3iii | 2.369 (3) | Cu3a—Se1cx | 2.575 (7) |
Cu1a—Se1c | 2.380 (5) | Cu3b—Se1axi | 2.461 (6) |
Cu1a—Se1biv | 2.417 (5) | Cu3b—Se2vii | 2.476 (6) |
Cu1b—Se1dv | 2.439 (6) | Cu3b—Se1dvii | 2.541 (4) |
Cu1b—Se1bvi | 2.511 (4) | Cu3b—Se3xii | 2.599 (4) |
Cu1b—Se3vi | 2.523 (3) | Cu4a—Se2vi | 2.285 (6) |
Cu1b—Se2vi | 2.592 (6) | Cu4a—Se3xiii | 2.370 (7) |
Cu2—Se1dvii | 2.420 (5) | Cu4b—Se1bi | 2.413 (5) |
Cu2—Se2 | 2.437 (3) | Cu4b—Se1avii | 2.447 (6) |
Cu2—Se1c | 2.600 (5) | Cu4b—Se3 | 2.467 (7) |
Symmetry codes: (i) −x+1/2, y+1/2, z−1/2; (ii) −x, −y+1, z−1/2; (iii) −x+1/2, y−1/2, z+1/2; (iv) −x+1/2, y+1/2, z+1/2; (v) x+1, y, z−1; (vi) −x+1, −y+1, z−1/2; (vii) x+1/2, −y+3/2, z; (viii) x+1, y−1, z; (ix) −x+3/2, y−1/2, z−1/2; (x) x+1/2, −y+1/2, z−1; (xi) x+1/2, −y+3/2, z+1; (xii) −x+1, −y+2, z+1/2; (xiii) x+1/2, −y+1/2, z. |
Experimental details
Crystal data |
Chemical formula | Cu7PSe6 |
Mr | 949.6 |
Crystal system, space group | Orthorhombic, Pna21 |
Temperature (K) | ? |
a, b, c (Å) | 14.3179 (4), 7.1112 (2), 10.1023 (3) |
V (Å3) | 1028.59 (5) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 352.9 |
Crystal size (mm) | × × |
|
Data collection |
Diffractometer | STOE IPDS diffractometer |
Absorption correction | Spherical |
Tmin, Tmax | 0.053, 0.145 |
No. of measured, independent and observed (3) reflections | ?, 29369, 3714 |
Rint | ? |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.047, 0.080, 1.06 |
No. of reflections | 29369 |
No. of parameters | 127 |
No. of restraints | ? |
Δρmax, Δρmin (e Å−3) | 2.30, −2.02 |
Selected bond lengths (Å) topP—Se1a | 2.194 (5) | Cu2—Se3 | 2.755 (7) |
P—Se1ci | 2.195 (5) | Cu3a—Se2vi | 2.405 (6) |
P—Se1bi | 2.193 (5) | Cu3a—Se1aviii | 2.457 (4) |
P—Se1dii | 2.218 (5) | Cu3a—Se3ix | 2.509 (4) |
Cu1a—Se3iii | 2.369 (3) | Cu3a—Se1cx | 2.575 (7) |
Cu1a—Se1c | 2.380 (5) | Cu3b—Se1axi | 2.461 (6) |
Cu1a—Se1biv | 2.417 (5) | Cu3b—Se2vii | 2.476 (6) |
Cu1b—Se1dv | 2.439 (6) | Cu3b—Se1dvii | 2.541 (4) |
Cu1b—Se1bvi | 2.511 (4) | Cu3b—Se3xii | 2.599 (4) |
Cu1b—Se3vi | 2.523 (3) | Cu4a—Se2vi | 2.285 (6) |
Cu1b—Se2vi | 2.592 (6) | Cu4a—Se3xiii | 2.370 (7) |
Cu2—Se1dvii | 2.420 (5) | Cu4b—Se1bi | 2.413 (5) |
Cu2—Se2 | 2.437 (3) | Cu4b—Se1avii | 2.447 (6) |
Cu2—Se1c | 2.600 (5) | Cu4b—Se3 | 2.467 (7) |
Symmetry codes: (i) −x+1/2, y+1/2, z−1/2; (ii) −x, −y+1, z−1/2; (iii) −x+1/2, y−1/2, z+1/2; (iv) −x+1/2, y+1/2, z+1/2; (v) x+1, y, z−1; (vi) −x+1, −y+1, z−1/2; (vii) x+1/2, −y+3/2, z; (viii) x+1, y−1, z; (ix) −x+3/2, y−1/2, z−1/2; (x) x+1/2, −y+1/2, z−1; (xi) x+1/2, −y+3/2, z+1; (xii) −x+1, −y+2, z+1/2; (xiii) x+1/2, −y+1/2, z. |
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