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Crystal Lab › Prototype structures › Orthorhombic

MgB₂C₂

Orthorhombic · space group Cmce (No. 64) · Pearson oC80

Symmetry elements and Wyckoff positions (interactive)

MgB₂C₂ in Cmce

Setting
Loading the group…
x = 0.10, y = 0.17, z = 0.08

Unit 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

SiteElementWyckoffMultiplicityxyz
Mg7Mg8d80.84660.00000.0000
B1B8e80.25000.40540.2500
C4C8e80.25000.57290.2500
B2B8f80.00000.08860.7760
C5C8f80.00000.42080.7314
Mg8Mg8f80.00000.77980.4887
B3B16g160.12780.84150.7438
C6C16g160.12450.67500.7231

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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