Crystal Lab › Prototype structures › Trigonal
Sn₄As₃
Trigonal · space group R3m (No. 160) · Pearson hR7
Symmetry elements and Wyckoff positions (interactive)
Sn₄As₃ in R3m
SettingUnit cell
- Lattice constants
- a = 4.089 Å, b = 4.089 Å, c = 36.059 Å; α = 90.00°, β = 90.00°, γ = 120.00°
- Cell volume
- 522.1 ų
- Atoms in the conventional cell
- 21 (As 9, Sn 12)
- Formula units Z
- 3
- Pearson symbol
- hR7 — hexagonal / trigonal, rhombohedral lattice, 7 atoms per conventional cell
- Symmetry operations
- 18 per cell
Crystallographic sites
| Site | Element | Wyckoff | Multiplicity | x | y | z |
|---|---|---|---|---|---|---|
| As1 | As | 3a | 3 | 0.0000 | 0.0000 | 0.5724 |
| As2 | As | 3a | 3 | 0.0000 | 0.0000 | 0.0027 |
| As3 | As | 3a | 3 | 0.0000 | 0.0000 | 0.4323 |
| Sn4 | Sn | 3a | 3 | 0.0000 | 0.0000 | 0.2907 |
| Sn5 | Sn | 3a | 3 | 0.0000 | 0.0000 | 0.7131 |
| Sn6 | Sn | 3a | 3 | 0.0000 | 0.0000 | 0.1378 |
| Sn7 | Sn | 3a | 3 | 0.0000 | 0.0000 | 0.8660 |
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 21 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
A3B4_hR7_160_3a_4a-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol hR7, then the space-group number 160, then the Wyckoff letters occupied by each element in turn (As: 3a; As: 3a; As: 3a; Sn: 3a; Sn: 3a; Sn: 3a; Sn: 3a). 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 A3B4_hR7_160_3a_4a-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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