Unit cell
- Lattice constants
- a = 8.080 Å, b = 8.080 Å, c = 8.080 Å; α = 90°, β = 90°, γ = 90°
- Cell volume
- 527.5 ų
- Atoms in the cell
- 56 (Mg 8, Al 16, O 32)
- Formula units Z
- 8
- Calculated density
- 3.58 g cm⁻³
- Shortest contact
- 1.917 Å
Coordination
- Mg
- CN 4 at 1.92 Å (4 O)
- Al
- CN 6 at 1.93 Å (6 O)
- O
- CN 4 at 1.92 Å (1 Mg + 3 Al)
About the structure
- ccp array of O²⁻ (32 per cell): A²⁺ (Mg) in ⅛ of the tetrahedral holes, B³⁺ (Al) in ½ of the octahedral holes.
- Coordination: Mg 4, Al 6, O 4 (1 Mg + 3 Al).
- Inverse spinel (e.g. Fe₃O₄, Mg₂TiO₄): half the B cations take the tetrahedral sites and A moves to octahedral sites — same framework, different cation distribution.
- Many ferrites (MFe₂O₄) and the Li-ion cathode LiMn₂O₄ are spinels.
Atom positions (fractional, one cell)
| Atom | x | y | z |
|---|---|---|---|
| Mg | 0.0000 | 0.0000 | 0.0000 |
| Mg | 0.0000 | 0.5000 | 0.5000 |
| Mg | 0.5000 | 0.0000 | 0.5000 |
| Mg | 0.5000 | 0.5000 | 0.0000 |
| Mg | 0.7500 | 0.2500 | 0.7500 |
| Mg | 0.7500 | 0.7500 | 0.2500 |
| Mg | 0.2500 | 0.2500 | 0.2500 |
| Mg | 0.2500 | 0.7500 | 0.7500 |
| Al | 0.6250 | 0.6250 | 0.6250 |
| Al | 0.6250 | 0.1250 | 0.1250 |
| Al | 0.1250 | 0.6250 | 0.1250 |
| Al | 0.1250 | 0.1250 | 0.6250 |
| Al | 0.3750 | 0.8750 | 0.1250 |
| Al | 0.3750 | 0.3750 | 0.6250 |
| Al | 0.8750 | 0.8750 | 0.6250 |
| Al | 0.8750 | 0.3750 | 0.1250 |
| Al | 0.8750 | 0.1250 | 0.3750 |
| Al | 0.8750 | 0.6250 | 0.8750 |
| Al | 0.3750 | 0.1250 | 0.8750 |
| Al | 0.3750 | 0.6250 | 0.3750 |
| Al | 0.1250 | 0.3750 | 0.8750 |
| Al | 0.1250 | 0.8750 | 0.3750 |
| Al | 0.6250 | 0.3750 | 0.3750 |
| Al | 0.6250 | 0.8750 | 0.8750 |
| O | 0.3870 | 0.3870 | 0.3870 |
| O | 0.3870 | 0.8870 | 0.8870 |
| O | 0.8870 | 0.3870 | 0.8870 |
| O | 0.8870 | 0.8870 | 0.3870 |
| O | 0.6130 | 0.1130 | 0.8870 |
| O | 0.6130 | 0.6130 | 0.3870 |
| O | 0.1130 | 0.1130 | 0.3870 |
| O | 0.1130 | 0.6130 | 0.8870 |
| O | 0.1130 | 0.8870 | 0.6130 |
| O | 0.1130 | 0.3870 | 0.1130 |
| O | 0.6130 | 0.8870 | 0.1130 |
| O | 0.6130 | 0.3870 | 0.6130 |
| O | 0.8870 | 0.6130 | 0.1130 |
| O | 0.8870 | 0.1130 | 0.6130 |
| O | 0.3870 | 0.6130 | 0.6130 |
| O | 0.3870 | 0.1130 | 0.1130 |
| O | 0.1370 | 0.6370 | 0.3630 |
| O | 0.1370 | 0.1370 | 0.8630 |
| O | 0.6370 | 0.6370 | 0.8630 |
| O | 0.6370 | 0.1370 | 0.3630 |
| O | 0.8630 | 0.8630 | 0.8630 |
| O | 0.8630 | 0.3630 | 0.3630 |
| O | 0.3630 | 0.8630 | 0.3630 |
| O | 0.3630 | 0.3630 | 0.8630 |
| O | 0.6370 | 0.3630 | 0.1370 |
| O | 0.6370 | 0.8630 | 0.6370 |
| O | 0.1370 | 0.3630 | 0.6370 |
| O | 0.1370 | 0.8630 | 0.1370 |
| O | 0.3630 | 0.1370 | 0.6370 |
| O | 0.3630 | 0.6370 | 0.1370 |
| O | 0.8630 | 0.1370 | 0.1370 |
| O | 0.8630 | 0.6370 | 0.6370 |
Z, coordination numbers, distances, density and packing on this page are computed from these coordinates.
Other oxides & frameworks
Perovskite (ideal cubic)SrTiO₃ · ABO₃Rhenium trioxideReO₃ · AB₃CorundumAl₂O₃ · A₂B₃CupriteCu₂O · A₂BPyriteFeS₂ · AB₂ with S₂²⁻ pairsCalciteCaCO₃ · CarbonateMolybdeniteMoS₂ · Layered AB₂, 6:3ScheeliteCaWO₄ · ABO₄ tetrahedral oxo-anionMagnetite (inverse spinel)Fe₃O₄ · Inverse spinel AB₂O₄Ice Ih (oxygen framework)H₂O · Hydrogen-bonded network