Crystal Lab › Prototype structures › Orthorhombic
MgB₂C₂
Orthorhombic · space group Cmce (No. 64) · Pearson oC80
Symmetry elements and Wyckoff positions (interactive)
MgB₂C₂ in Cmce
SettingUnit cell
- Lattice constants
- a = 10.922 Å, b = 9.461 Å, c = 7.459 Å; α = 90.00°, β = 90.00°, γ = 90.00°
- Cell volume
- 770.8 ų
- Atoms in the conventional cell
- 80 (Mg 16, B 32, C 32)
- Formula units Z
- 16
- Pearson symbol
- oC80 — orthorhombic, base-centred lattice, 80 atoms per conventional cell
- Symmetry operations
- 16 per cell
Crystallographic sites
| Site | Element | Wyckoff | Multiplicity | x | y | z |
|---|---|---|---|---|---|---|
| Mg7 | Mg | 8d | 8 | 0.8466 | 0.0000 | 0.0000 |
| B1 | B | 8e | 8 | 0.2500 | 0.4054 | 0.2500 |
| C4 | C | 8e | 8 | 0.2500 | 0.5729 | 0.2500 |
| B2 | B | 8f | 8 | 0.0000 | 0.0886 | 0.7760 |
| C5 | C | 8f | 8 | 0.0000 | 0.4208 | 0.7314 |
| Mg8 | Mg | 8f | 8 | 0.0000 | 0.7798 | 0.4887 |
| B3 | B | 16g | 16 | 0.1278 | 0.8415 | 0.7438 |
| C6 | C | 16g | 16 | 0.1245 | 0.6750 | 0.7231 |
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 80 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
A2B2C_oC80_64_efg_efg_df-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol oC80, then the space-group number 64, then the Wyckoff letters occupied by each element in turn (Mg: 8d; B: 8e; C: 8e; B: 8f; C: 8f; Mg: 8f; B: 16g; C: 16g). 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 A2B2C_oC80_64_efg_efg_df-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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