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Crystal Lab › Prototype structures › Orthorhombic

Cr₄AlB₆

Orthorhombic · space group Cmmm (No. 65) · Pearson oC22

Symmetry elements and Wyckoff positions (interactive)

Cr₄AlB₆ in Cmmm

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

Unit cell

Lattice constants
a = 21.280 Å, b = 2.952 Å, c = 3.013 Å; α = 90.00°, β = 90.00°, γ = 90.00°
Cell volume
189.3 ų
Atoms in the conventional cell
22 (Al 2, B 12, Cr 8)
Formula units Z
2
Pearson symbol
oC22 — orthorhombic, base-centred lattice, 22 atoms per conventional cell
Symmetry operations
16 per cell

Crystallographic sites

SiteElementWyckoffMultiplicityxyz
Al1Al2a20.00000.00000.0000
B2B4g40.10500.00000.0000
B3B4g40.64810.00000.0000
B4B4g40.72980.00000.0000
Cr5Cr4h40.57630.00000.5000
Cr6Cr4h40.18840.00000.5000

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 22 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

AB6C4_oC22_65_a_3g_2h-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol oC22, then the space-group number 65, then the Wyckoff letters occupied by each element in turn (Al: 2a; B: 4g; B: 4g; B: 4g; Cr: 4h; Cr: 4h). 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 AB6C4_oC22_65_a_3g_2h-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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