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Crystal Lab › Prototype structures › Orthorhombic

SrSn₄

Orthorhombic · space group Cmcm (No. 63) · Pearson oC20

Symmetry elements and Wyckoff positions (interactive)

SrSn₄ in Cmcm

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

Unit cell

Lattice constants
a = 4.618 Å, b = 17.372 Å, c = 7.060 Å; α = 90.00°, β = 90.00°, γ = 90.00°
Cell volume
566.4 ų
Atoms in the conventional cell
20 (Sn 16, Sr 4)
Formula units Z
4
Pearson symbol
oC20 — orthorhombic, base-centred lattice, 20 atoms per conventional cell
Symmetry operations
16 per cell

Crystallographic sites

SiteElementWyckoffMultiplicityxyz
Sn1Sn4a40.00000.00000.0000
Sn2Sn4c40.00000.59020.2500
Sr4Sr4c40.00000.38820.2500
Sn3Sn8f80.00000.19590.0447

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 20 atoms drawn above are these sites multiplied by all 16 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

A4B_oC20_63_acf_c-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol oC20, then the space-group number 63, then the Wyckoff letters occupied by each element in turn (Sn: 4a; Sn: 4c; Sr: 4c; Sn: 8f). 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 A4B_oC20_63_acf_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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