Crystal Lab › Prototype structures › Orthorhombic
LaCa₂Mn₂O₇
Orthorhombic · space group Cmcm (No. 63) · Pearson oC48
Symmetry elements and Wyckoff positions (interactive)
LaCa₂Mn₂O₇ in Cmcm
SettingUnit cell
- Lattice constants
- a = 19.202 Å, b = 5.456 Å, c = 5.415 Å; α = 90.00°, β = 90.00°, γ = 90.00°
- Cell volume
- 567.3 ų
- Atoms in the conventional cell
- 48 (La 4, O 28, Ca 8, Mn 8)
- Formula units Z
- 4
- Pearson symbol
- oC48 — orthorhombic, base-centred lattice, 48 atoms per conventional cell
- Symmetry operations
- 16 per cell
Crystallographic sites
| Site | Element | Wyckoff | Multiplicity | x | y | z |
|---|---|---|---|---|---|---|
| La2 | La | 4c | 4 | 0.0000 | 0.2503 | 0.2500 |
| O4 | O | 4c | 4 | 0.0000 | 0.6986 | 0.2500 |
| O5 | O | 8e | 8 | 0.3928 | 0.0000 | 0.0000 |
| O6 | O | 8e | 8 | 0.0883 | 0.0000 | 0.0000 |
| Ca1 | Ca | 8g | 8 | 0.3156 | 0.7348 | 0.2500 |
| Mn3 | Mn | 8g | 8 | 0.3997 | 0.2500 | 0.2500 |
| O7 | O | 8g | 8 | 0.3013 | 0.2906 | 0.2500 |
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 48 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
A2BC2D7_oC48_63_g_c_g_c2eg-001: the stoichiometry comes first (A, B, C… are the elements in alphabetical order of their site labels), then the Pearson symbol oC48, then the space-group number 63, then the Wyckoff letters occupied by each element in turn (La: 4c; O: 4c; O: 8e; O: 8e; Ca: 8g; Mn: 8g; O: 8g). Two structures with the same label are the same arrangement with different cell parameters or coordinates.
Other compounds with this structure
BaEu₂Mn₂O₇, LaRb₂Mn₂O₇, PrCa₂Mn₂O₇, SrGd₂Co₂O₇ <!--beginning with an
Source
Coordinates and cell from the AFLOW Encyclopedia of Crystallographic Prototypes, entry A2BC2D7_oC48_63_g_c_g_c2eg-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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