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Crystal Lab › Prototype structures › Trigonal

Moissanite 9R (CSi)

Trigonal · space group R3m (No. 160) · Pearson hR6 · mineral: moissanite

Symmetry elements and Wyckoff positions (interactive)

Moissanite 9R (CSi) in R3m

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

Unit cell

Lattice constants
a = 3.018 Å, b = 3.018 Å, c = 22.177 Å; α = 90.00°, β = 90.00°, γ = 120.00°
Cell volume
174.9 ų
Atoms in the conventional cell
18 (C 9, Si 9)
Formula units Z
9
Pearson symbol
hR6 — hexagonal / trigonal, rhombohedral lattice, 6 atoms per conventional cell
Symmetry operations
18 per cell

Crystallographic sites

SiteElementWyckoffMultiplicityxyz
C1C3a30.00000.00000.0000
C2C3a30.00000.00000.2222
C3C3a30.00000.00000.7778
Si4Si3a30.00000.00000.0833
Si5Si3a30.00000.00000.3056
Si6Si3a30.00000.00000.8611

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 18 atoms drawn above are these sites multiplied by all 18 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

AB_hR6_160_3a_3a-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol hR6, then the space-group number 160, then the Wyckoff letters occupied by each element in turn (C: 3a; C: 3a; C: 3a; Si: 3a; Si: 3a; Si: 3a). Two structures with the same label are the same arrangement with different cell parameters or coordinates.

Other compounds with this structure

ZnS <!--beginning with an

Note: 9R Moissanite.

Source

Coordinates and cell from the AFLOW Encyclopedia of Crystallographic Prototypes, entry AB_hR6_160_3a_3a-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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