Crystal Lab › Prototype structures › Orthorhombic
MgCuAl₂ (E1_{a})
Orthorhombic · space group Cmcm (No. 63) · Pearson oC16 · Strukturbericht E1a
Symmetry elements and Wyckoff positions (interactive)
MgCuAl₂ (E1_{a}) in Cmcm
SettingUnit cell
- Lattice constants
- a = 4.012 Å, b = 9.265 Å, c = 7.124 Å; α = 90.00°, β = 90.00°, γ = 90.00°
- Cell volume
- 264.8 ų
- Atoms in the conventional cell
- 16 (Cu 4, Mg 4, Al 8)
- 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 |
|---|---|---|---|---|---|---|
| Cu2 | Cu | 4c | 4 | 0.0000 | 0.7801 | 0.2500 |
| Mg3 | Mg | 4c | 4 | 0.0000 | 0.0651 | 0.2500 |
| Al1 | Al | 8f | 8 | 0.0000 | 0.3558 | 0.0556 |
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_63_f_c_c-002: 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 63, then the Wyckoff letters occupied by each element in turn (Cu: 4c; Mg: 4c; Al: 8f). Two structures with the same label are the same arrangement with different cell parameters or coordinates.
Other compounds with this structure
CaNiGa₂, CeCuPd₂, EuIrSn₂, EuPdIn₂, EuPdSn₂, LaPdIn₂, NdCuPd₂, PPdNi₂, PdSrMg₂, PrCuPd₂, ScNiAl₂, SmCuPd₂, TaBCo₂, YNiAl₂, YbAuIn₂, YbPdIn₂ <!--beginning with an
Note: E1_{a}.
Source
Coordinates and cell from the AFLOW Encyclopedia of Crystallographic Prototypes, entry A2BC_oC16_63_f_c_c-002 (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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