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Crystal Lab › Prototype structures › Orthorhombic

HgBr₂ (C24)

Orthorhombic · space group Cmc21 (No. 36) · Pearson oC12 · Strukturbericht C24

Symmetry elements and Wyckoff positions (interactive)

HgBr₂ (C24) in Cmc21

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

Unit cell

Lattice constants
a = 4.624 Å, b = 6.789 Å, c = 12.445 Å; α = 90.00°, β = 90.00°, γ = 90.00°
Cell volume
390.7 ų
Atoms in the conventional cell
12 (Br 8, Hg 4)
Formula units Z
4
Pearson symbol
oC12 — orthorhombic, base-centred lattice, 12 atoms per conventional cell
Symmetry operations
8 per cell

Crystallographic sites

SiteElementWyckoffMultiplicityxyz
Br1Br4a40.00000.06100.1340
Br2Br4a40.00000.39500.3660
Hg3Hg4a40.00000.33300.0000

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 12 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

A2B_oC12_36_2a_a-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol oC12, then the space-group number 36, then the Wyckoff letters occupied by each element in turn (Br: 4a; Br: 4a; Hg: 4a). Two structures with the same label are the same arrangement with different cell parameters or coordinates.

Other compounds with this structure

β-HgI₂ <!--beginning with an

Note: C24.

Source

Coordinates and cell from the AFLOW Encyclopedia of Crystallographic Prototypes, entry A2B_oC12_36_2a_a-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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