Study of the incommensurately modulated structure of Cs2CdBr4 by single-crystal diffraction
Authors:Speziali, N.L.; Chapuis, G.
Journal:Acta Cryst. B 45 20-26 (1989)
DOI:https://doi.org/10.1107/S0108768188009279
B-IncStrDB ID: 432E08oB9 Entry date: 2010-11-08 Last revision: 2021-12-30
CsCd
Chemical data
Structural Formula Sum: Br4 Cd1 Cs2 [ Help ]
Formula weight: 697.8 Da [ Help ]
Crystallographic data and experimental details
a: 10.205(4) Å [ Help ]
b: 7.887(3) Å [ Help ]
c: 13.925(7) Å [ Help ]
α: 90 ° [ Help ]
β: 90 ° [ Help ]
γ: 90 ° [ Help ]
Volume: 1120.8(8) Å3 [ Help ]
Z: 4 [ Help ]
μ: 81.622 mm-1 [ Help ]
Cell measurement temperature: 245 K [ Help ]
Crystal system: orthorhombic [ Help ]
Superspace group name (WJJ): P:P n m a:-1 s s [ Help ]
Superspace group name: Pnma(α00)0ss [ Help ]
Symmetry operations of the superspace group: (Show/hide table) [ Help ]
| Operation code | Operation in algebraic form |
|---|---|
| 1 | x1,x2,x3,x4 |
| 2 | x1,1/2-x2,x3,1/2+x4 |
| 3 | 1/2+x1,x2,1/2-x3,1/2+x4 |
| 4 | 1/2+x1,1/2-x2,1/2-x3,x4 |
| 5 | -x1,-x2,-x3,-x4 |
| 6 | -x1,1/2+x2,-x3,1/2-x4 |
| 7 | 1/2-x1,-x2,1/2+x3,1/2-x4 |
| 8 | 1/2-x1,1/2+x2,1/2+x3,-x4 |
Space group name (H-M): P n m a [ Help ]
Modulation dimension: 1 [ Help ]
Measured independent wave vectors: (Show/hide table) [ Help ]
| Wave vector id | q_x | q_y | q_z |
|---|---|---|---|
| 1 | 0.170(3) | 0 | 0 |
Refinement details
Modulation functions description: Displacive modulation: Fourier series.1st-order harmonics. [ Help ]
Structure factors calc. details: Gaussian integration [ Help ]
Nb. of observed reflections: 578 [ Help ]
R(obs): 0.054 [ Help ]
Structural Information
Average Structure: (Show/hide table) [ Help ]
| Atom site label | Atom symbol | Symmetry multiplicity | Occupancy | x | y | z | Uiso/equiv | ADP type |
|---|---|---|---|---|---|---|---|---|
| Cs1 | Cs | 4 | 1 | 0.1234(2) | 0.25 | 0.0976(2) | ? | Uani |
| Cs2 | Cs | 4 | 1 | -0.0165(2) | 0.25 | 0.6759(1) | ? | Uani |
| Cd | Cd | 4 | 1 | 0.2223(2) | 0.25 | 0.4238(3) | ? | Uani |
| Br1 | Br | 4 | 1 | -0.0252(4) | 0.25 | 0.4126(3) | ? | Uani |
| Br2 | Br | 4 | 1 | 0.3219(4) | 0.25 | 0.5926(3) | ? | Uani |
| Br3 | Br | 8 | 1 | 0.3196(3) | -0.0083(5) | 0.3412(3) | ? | Uani |
Fourier Wave Vectors (explicit: q_x,q_y,q_z or coefficients: q_1,q_2,...): (Show/hide table) [ Help ]
| Wave vector code | q_x | q_y | q_z |
|---|---|---|---|
| 1 | 0.170 | 0 | 0 |
Definition of the displacive (translational) Fourier series: (Show/hide table) [ Help ]
| Modulation code | Atom site label | Displacement axis | Wave vector code |
|---|---|---|---|
| Cs1y1 | Cs1 | y | 1 |
| Cs2y1 | Cs2 | y | 1 |
| Cdy1 | Cd | y | 1 |
| Br1y1 | Br1 | y | 1 |
| Br2y1 | Br2 | y | 1 |
| Br3x1 | Br3 | x | 1 |
| Br3y1 | Br3 | y | 1 |
| Br3z1 | Br3 | z | 1 |
Displacive (translational) Fourier coefficients: (Show/hide table) [ Help ]
| Modulation code | Cosine coefficient | Sine coefficient |
|---|---|---|
| Cs1y1 | 0.0076(11) | -0.0034(11) |
| Cs2y1 | 0.0074(9) | -0.0039(10) |
| Cdy1 | -0.0026(8) | 0.0031(9) |
| Br1y1 | 0.0021(21) | 0.0112(26) |
| Br2y1 | 0.0296(20) | 0.0016(31) |
| Br3x1 | 0.0046(11) | -0.0029(10) |
| Br3y1 | -0.0170(12) | 0.0020(20) |
| Br3z1 | 0.0188(6) | 0.0001(10) |