Crystal Lab › Prototype structures › Orthorhombic
Nb₄As₃
Orthorhombic · space group Cmcm (No. 63) · Pearson oC56
Symmetry elements and Wyckoff positions (interactive)
Nb₄As₃ in Cmcm
SettingUnit cell
- Lattice constants
- a = 3.516 Å, b = 14.660 Å, c = 18.830 Å; α = 90.00°, β = 90.00°, γ = 90.00°
- Cell volume
- 970.6 ų
- Atoms in the conventional cell
- 56 (Nb 32, As 24)
- Formula units Z
- 8
- Pearson symbol
- oC56 — orthorhombic, base-centred lattice, 56 atoms per conventional cell
- Symmetry operations
- 16 per cell
Crystallographic sites
| Site | Element | Wyckoff | Multiplicity | x | y | z |
|---|---|---|---|---|---|---|
| Nb5 | Nb | 4a | 4 | 0.0000 | 0.0000 | 0.0000 |
| As1 | As | 4c | 4 | 0.0000 | 0.3076 | 0.2500 |
| As2 | As | 4c | 4 | 0.0000 | 0.5879 | 0.2500 |
| Nb6 | Nb | 4c | 4 | 0.0000 | 0.9468 | 0.2500 |
| As3 | As | 8f | 8 | 0.0000 | 0.0982 | 0.8821 |
| As4 | As | 8f | 8 | 0.0000 | 0.1577 | 0.0772 |
| Nb7 | Nb | 8f | 8 | 0.0000 | 0.2624 | 0.8382 |
| Nb8 | Nb | 8f | 8 | 0.0000 | 0.4662 | 0.8800 |
| Nb9 | Nb | 8f | 8 | 0.0000 | 0.3318 | 0.0285 |
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 56 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
A3B4_oC56_63_2c2f_ac3f-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol oC56, then the space-group number 63, then the Wyckoff letters occupied by each element in turn (Nb: 4a; As: 4c; As: 4c; Nb: 4c; As: 8f; As: 8f; Nb: 8f; Nb: 8f; Nb: 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 A3B4_oC56_63_2c2f_ac3f-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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