Crystal Lab › Prototype structures › Orthorhombic
Al₂CuIr
Orthorhombic · space group Cmme (No. 67) · Pearson oC16
Symmetry elements and Wyckoff positions (interactive)
Al₂CuIr in Cmme
SettingUnit cell
- Lattice constants
- a = 5.065 Å, b = 8.120 Å, c = 5.185 Å; α = 90.00°, β = 90.00°, γ = 90.00°
- Cell volume
- 213.2 ų
- Atoms in the conventional cell
- 16 (Al 8, Cu 4, Ir 4)
- Formula units Z
- 4
- Pearson symbol
- oC16 — orthorhombic, base-centred lattice, 16 atoms per conventional cell
- Symmetry operations
- 16 per cell
Crystallographic sites
| Site | Element | Wyckoff | Multiplicity | x | y | z |
|---|---|---|---|---|---|---|
| Al1 | Al | 4a | 4 | 0.2500 | 0.0000 | 0.0000 |
| Cu3 | Cu | 4b | 4 | 0.2500 | 0.0000 | 0.5000 |
| Al2 | Al | 4g | 4 | 0.0000 | 0.2500 | 0.3305 |
| Ir4 | Ir | 4g | 4 | 0.0000 | 0.2500 | 0.8198 |
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 16 atoms drawn above are these sites multiplied by all 16 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
A2BC_oC16_67_ag_b_g-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol oC16, then the space-group number 67, then the Wyckoff letters occupied by each element in turn (Al: 4a; Cu: 4b; Al: 4g; Ir: 4g). Two structures with the same label are the same arrangement with different cell parameters or coordinates.
Source
Coordinates and cell from the AFLOW Encyclopedia of Crystallographic Prototypes, entry A2BC_oC16_67_ag_b_g-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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