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Crystal Lab › Prototype structures › Tetragonal

Tl₄HgI₆

Tetragonal · space group P4nc (No. 104) · Pearson tP22

Symmetry elements and Wyckoff positions (interactive)

Tl₄HgI₆ in P4nc

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

Unit cell

Lattice constants
a = 9.394 Å, b = 9.394 Å, c = 9.222 Å; α = 90.00°, β = 90.00°, γ = 90.00°
Cell volume
813.8 ų
Atoms in the conventional cell
22 (Hg 2, I 12, Tl 8)
Formula units Z
2
Pearson symbol
tP22 — tetragonal, primitive lattice, 22 atoms per conventional cell
Symmetry operations
8 per cell

Crystallographic sites

SiteElementWyckoffMultiplicityxyz
Hg1Hg2a20.00000.00000.7860
I2I2a20.00000.00000.5000
I3I2a20.00000.00000.0649
I4I8c80.82970.64580.2860
Tl5Tl8c80.64910.85880.0360

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 22 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

AB6C4_tP22_104_a_2ac_c-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol tP22, then the space-group number 104, then the Wyckoff letters occupied by each element in turn (Hg: 2a; I: 2a; I: 2a; I: 8c; Tl: 8c). 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 AB6C4_tP22_104_a_2ac_c-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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