Crystal Lab › Prototype structures › Orthorhombic
H₂S (170 GPa)
Orthorhombic · space group Cmce (No. 64) · Pearson oC24
Symmetry elements and Wyckoff positions (interactive)
H₂S (170 GPa) in Cmce
SettingUnit cell
- Lattice constants
- a = 2.999 Å, b = 4.327 Å, c = 7.601 Å; α = 90.00°, β = 90.00°, γ = 90.00°
- Cell volume
- 98.6 ų
- Atoms in the conventional cell
- 24 (H 16, S 8)
- Formula units Z
- 8
- Pearson symbol
- oC24 — orthorhombic, base-centred lattice, 24 atoms per conventional cell
- Symmetry operations
- 16 per cell
Crystallographic sites
| Site | Element | Wyckoff | Multiplicity | x | y | z |
|---|---|---|---|---|---|---|
| H1 | H | 8f | 8 | 0.0000 | 0.3720 | 0.2700 |
| H2 | H | 8f | 8 | 0.0000 | 0.6000 | 0.0920 |
| S3 | S | 8f | 8 | 0.0000 | 0.3710 | 0.6150 |
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 24 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
A2B_oC24_64_2f_f-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol oC24, then the space-group number 64, then the Wyckoff letters occupied by each element in turn (H: 8f; H: 8f; S: 8f). Two structures with the same label are the same arrangement with different cell parameters or coordinates.
Note: HP, Theory.
Source
Coordinates and cell from the AFLOW Encyclopedia of Crystallographic Prototypes, entry A2B_oC24_64_2f_f-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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