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Crystal Lab › Prototype structures › Orthorhombic

Ni₃Si₂

Orthorhombic · space group Cmc21 (No. 36) · Pearson oC80

Symmetry elements and Wyckoff positions (interactive)

Ni₃Si₂ in Cmc21

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

Unit cell

Lattice constants
a = 12.229 Å, b = 10.805 Å, c = 6.924 Å; α = 90.00°, β = 90.00°, γ = 90.00°
Cell volume
914.9 ų
Atoms in the conventional cell
80 (Ni 48, Si 32)
Formula units Z
16
Pearson symbol
oC80 — orthorhombic, base-centred lattice, 80 atoms per conventional cell
Symmetry operations
8 per cell

Crystallographic sites

SiteElementWyckoffMultiplicityxyz
Ni1Ni4a40.00000.00000.0000
Ni2Ni4a40.00000.23450.0240
Ni3Ni4a40.00000.23300.4000
Ni4Ni4a40.00000.38140.7140
Si10Si4a40.00000.40900.2180
Si9Si4a40.00000.15700.7120
Ni5Ni8b80.67320.61770.5180
Ni6Ni8b80.67230.61890.9000
Ni7Ni8b80.19720.24670.2170
Ni8Ni8b80.18240.49750.2250
Si11Si8b80.62000.55900.2140
Si12Si8b80.15200.34400.5060
Si13Si8b80.15100.34300.9200

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 80 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

A3B2_oC80_36_4a4b_2a3b-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol oC80, then the space-group number 36, then the Wyckoff letters occupied by each element in turn (Ni: 4a; Ni: 4a; Ni: 4a; Ni: 4a; Si: 4a; Si: 4a; Ni: 8b; Ni: 8b; Ni: 8b; Ni: 8b; Si: 8b; Si: 8b; Si: 8b). 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 A3B2_oC80_36_4a4b_2a3b-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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