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Crystal Lab › Prototype structures › Orthorhombic

Al₂CuIr

Orthorhombic · space group Cmme (No. 67) · Pearson oC16

Symmetry elements and Wyckoff positions (interactive)

Al₂CuIr in Cmme

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

Unit 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

SiteElementWyckoffMultiplicityxyz
Al1Al4a40.25000.00000.0000
Cu3Cu4b40.25000.00000.5000
Al2Al4g40.00000.25000.3305
Ir4Ir4g40.00000.25000.8198

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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