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Crystal Lab › Prototype structures › Orthorhombic

α-NiI₄ I₄Nb

Orthorhombic · space group Cmc21 (No. 36) · Pearson oC40

Symmetry elements and Wyckoff positions (interactive)

α-NiI₄ in Cmc21

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

Unit cell

Lattice constants
a = 7.670 Å, b = 13.230 Å, c = 13.930 Å; α = 90.00°, β = 90.00°, γ = 90.00°
Cell volume
1413.5 ų
Atoms in the conventional cell
40 (I 32, Nb 8)
Formula units Z
8
Pearson symbol
oC40 — orthorhombic, base-centred lattice, 40 atoms per conventional cell
Symmetry operations
8 per cell

Crystallographic sites

SiteElementWyckoffMultiplicityxyz
I1I4a40.00000.26080.0333
I2I4a40.00000.74360.0440
I3I4a40.00000.98870.2096
I4I4a40.00000.50660.1999
I5I8b80.24670.00610.9677
I6I8b80.24580.23340.2842
Nb7Nb8b80.21710.12560.1207

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 40 atoms drawn above are these sites multiplied by all 8 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

A4B_oC40_36_4a2b_b-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol oC40, then the space-group number 36, then the Wyckoff letters occupied by each element in turn (I: 4a; I: 4a; I: 4a; I: 4a; I: 8b; I: 8b; Nb: 8b). Two structures with the same label are the same arrangement with different cell parameters or coordinates.

Note: α-NiI₄.

Source

Coordinates and cell from the AFLOW Encyclopedia of Crystallographic Prototypes, entry A4B_oC40_36_4a2b_b-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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