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Crystal Lab › Prototype structures › Tetragonal

α-SrBr₂ Br₂Sr

Tetragonal · space group P4/n (No. 85) · Pearson tP30

Symmetry elements and Wyckoff positions (interactive)

α-SrBr₂ in P4/n

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

Unit cell

Lattice constants
a = 11.604 Å, b = 11.604 Å, c = 7.131 Å; α = 90.00°, β = 90.00°, γ = 90.00°
Cell volume
960.2 ų
Atoms in the conventional cell
30 (Br 20, Sr 10)
Formula units Z
10
Pearson symbol
tP30 — tetragonal, primitive lattice, 30 atoms per conventional cell
Symmetry operations
8 per cell

Crystallographic sites

SiteElementWyckoffMultiplicityxyz
Br1Br2a20.25000.75000.0000
Br2Br2b20.25000.75000.5000
Sr5Sr2c20.25000.25000.1471
Br3Br8g80.65310.95890.6229
Br4Br8g80.83890.95800.0996
Sr6Sr8g80.60570.08850.2491

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 30 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_tP30_85_ab2g_cg-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol tP30, then the space-group number 85, then the Wyckoff letters occupied by each element in turn (Br: 2a; Br: 2b; Sr: 2c; Br: 8g; Br: 8g; Sr: 8g). Two structures with the same label are the same arrangement with different cell parameters or coordinates.

Other compounds with this structure

EuBr{2}, α-Se₂U <!--beginning with an

Note: α-SrBr₂.

Source

Coordinates and cell from the AFLOW Encyclopedia of Crystallographic Prototypes, entry A2B_tP30_85_ab2g_cg-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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