Crystal Lab › Prototype structures › Tetragonal
α-SrBr₂ Br₂Sr
Tetragonal · space group P4/n (No. 85) · Pearson tP30
Symmetry elements and Wyckoff positions (interactive)
α-SrBr₂ in P4/n
SettingUnit cell
- Lattice constants
- a = 11.604 Å, b = 11.604 Å, c = 7.131 Å; α = 90.00°, β = 90.00°, γ = 90.00°
- Cell volume
- 960.2 ų
- Atoms in the conventional cell
- 30 (Br 20, Sr 10)
- Formula units Z
- 10
- Pearson symbol
- tP30 — tetragonal, primitive lattice, 30 atoms per conventional cell
- Symmetry operations
- 8 per cell
Crystallographic sites
| Site | Element | Wyckoff | Multiplicity | x | y | z |
|---|---|---|---|---|---|---|
| Br1 | Br | 2a | 2 | 0.2500 | 0.7500 | 0.0000 |
| Br2 | Br | 2b | 2 | 0.2500 | 0.7500 | 0.5000 |
| Sr5 | Sr | 2c | 2 | 0.2500 | 0.2500 | 0.1471 |
| Br3 | Br | 8g | 8 | 0.6531 | 0.9589 | 0.6229 |
| Br4 | Br | 8g | 8 | 0.8389 | 0.9580 | 0.0996 |
| Sr6 | Sr | 8g | 8 | 0.6057 | 0.0885 | 0.2491 |
The multiplicity and the Wyckoff letter say how many copies of the site the group makes in one cell and on which kind of symmetry element the site sits; the 30 atoms drawn above are these sites multiplied by all 8 operations. Press Wyckoff under Colour to see the sites, and tick a symmetry element on the left to see which atoms lie on it.
How to read the label
A2B_tP30_85_ab2g_cg-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol tP30, then the space-group number 85, then the Wyckoff letters occupied by each element in turn (Br: 2a; Br: 2b; Sr: 2c; Br: 8g; Br: 8g; Sr: 8g). Two structures with the same label are the same arrangement with different cell parameters or coordinates.
Other compounds with this structure
EuBr{2}, α-Se₂U <!--beginning with an
Note: α-SrBr₂.
Source
Coordinates and cell from the AFLOW Encyclopedia of Crystallographic Prototypes, entry A2B_tP30_85_ab2g_cg-001 (M. J. Mehl et al., Comput. Mater. Sci. 136, S1 (2017); D. Hicks et al., ibid. 161, S1 (2019) and 199, 110450 (2021); S. Eckert et al., ibid. 240, 112988 (2024)). Symmetry elements, Wyckoff assignment and the diagram are computed on this page from the group operations.
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