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Crystal Lab › Prototype structures › Trigonal

CdCl₂

Trigonal · space group R-3m (No. 166) · Pearson hR3

Symmetry elements and Wyckoff positions (interactive)

CdCl₂ in R-3m

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

Unit cell

Lattice constants
a = 3.995 Å, b = 3.995 Å, c = 17.749 Å; α = 90.00°, β = 90.00°, γ = 120.00°
Cell volume
245.3 ų
Atoms in the conventional cell
9 (Cd 3, Cl 6)
Formula units Z
3
Pearson symbol
hR3 — hexagonal / trigonal, rhombohedral lattice, 3 atoms per conventional cell
Symmetry operations
36 per cell

Crystallographic sites

SiteElementWyckoffMultiplicityxyz
Cd1Cd3a30.00000.00000.0000
Cl2Cl6c60.00000.00000.2500

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 9 atoms drawn above are these sites multiplied by all 36 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

AB2_hR3_166_a_c-004: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol hR3, then the space-group number 166, then the Wyckoff letters occupied by each element in turn (Cd: 3a; Cl: 6c). Two structures with the same label are the same arrangement with different cell parameters or coordinates.

Other compounds with this structure

(Ag_{x}Bi_{1-x})I₂, (Ag_{x}Sb_{1-x})I₂, C(Sc_{x}Y_{1-x})₂, CDy₂, CHo₂, CSc₂, CY₂, CdBr₂, CdCl₂, CoCl₂, FeCl₂, MgCl₂, MnBr₂, MnCl₂ (Sacchite), NbS₂, NiBr₂, NiCl₂, NiI₂, OCs₂, PbI₂, TaSe₂, ZnBr₂, ZnI₂ <!--beginning with an

Source

Coordinates and cell from the AFLOW Encyclopedia of Crystallographic Prototypes, entry AB2_hR3_166_a_c-004 (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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