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Crystal Lab › Prototype structures › Orthorhombic

HgCl₂ (C25)

Orthorhombic · space group Pnma (No. 62) · Pearson oP12 · Strukturbericht C25

Symmetry elements and Wyckoff positions (interactive)

HgCl₂ (C25) in Pnma

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

Unit cell

Lattice constants
a = 12.735 Å, b = 5.963 Å, c = 4.325 Å; α = 90.00°, β = 90.00°, γ = 90.00°
Cell volume
328.4 ų
Atoms in the conventional cell
12 (Cl 8, Hg 4)
Formula units Z
4
Pearson symbol
oP12 — orthorhombic, primitive lattice, 12 atoms per conventional cell
Symmetry operations
8 per cell

Crystallographic sites

SiteElementWyckoffMultiplicityxyz
Cl1Cl4c40.73300.25000.1250
Cl2Cl4c40.50800.25000.7220
Hg3Hg4c40.87400.25000.4470

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_oP12_62_2c_c-002: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol oP12, then the space-group number 62, then the Wyckoff letters occupied by each element in turn (Cl: 4c; Cl: 4c; Hg: 4c). Two structures with the same label are the same arrangement with different cell parameters or coordinates.

Other compounds with this structure

FeO₂ (goethite) <!--beginning with an

Note: C25.

Source

Coordinates and cell from the AFLOW Encyclopedia of Crystallographic Prototypes, entry A2B_oP12_62_2c_c-002 (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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