Al2O4
Al2O4 has a DFT band gap of 0.14–1.10 eV across 24 reported structures in 4 space groups; its lowest-energy polymorph is orthorhombic (Pnnm (No. 58)). Cross-validated across 3 computational databases.
At a glance
Key Properties
Cross-validated computational properties for Al2O4, aggregated across 3 databases.
Band GapEnergy needed to move an electron from the valence band to the conduction band. Lower or zero values tend to behave more metallic; larger gaps are more insulating or semiconducting.
0.14–1.10 eV
Range across DFT structures
Energy Above HullThermodynamic distance from the most stable set of competing phases. 0 eV/atom is on the convex hull; small positive values may still be experimentally accessible.
0.184 eV/atom
Best (lowest) across sources
StabilityA plain-language summary of the best reported energy-above-hull result. It reflects whether the lowest-energy structure is on, near, or far from the stability hull.
Above hull
1 DFT source
StructuresCount of reported calculated crystal structures for this formula, including alternate polymorphs, source databases, and observed space groups.
24
3 databases, 4 space groups
Crystallography
Reported Structures
Lowest-energy structures reported for Al2O4, ranked by energy above hull.
| Space GroupSymmetry classification of the crystal arrangement. The number is the international space-group index. | Crystal SystemBroad lattice family, such as cubic, tetragonal, monoclinic, or triclinic, derived from unit-cell symmetry. | Band Gap (eV)Electronic gap calculated for this specific reported structure, measured in electronvolts. | E above hull (eV/atom)Thermodynamic distance from the convex hull for this structure, normalized per atom. Lower is generally more stable. | E/atom (eV)Computed total energy normalized per atom. Use energy above hull, not this value alone, when comparing stability. | Density (g/cm³)Mass per relaxed crystal volume, reported in grams per cubic centimeter. |
|---|---|---|---|---|---|
| Pnnm (No. 58) | orthorhombic | 0.29 | 0.1842 | -7.218 | 3.62 |
| Pnma (No. 62) | orthorhombic | 0.14 | 0.2291 | -7.174 | 2.99 |
| Cmcm (No. 63) | orthorhombic | 0.00 | 0.2953 | -7.107 | 3.34 |
| Cmcm (No. 63) | orthorhombic | 0.00 | 0.3559 | -7.047 | 3.19 |
| Pnma (No. 62) | orthorhombic | 1.10 | 0.4353 | -6.967 | 2.95 |
| No. 0 | unknown | — | — | — | 0.76 |
| — | — | — | — | — | 3.63 |
| No. 0 | unknown | — | — | — | 0.83 |
| No. 0 | unknown | — | — | — | 0.83 |
| No. 0 | unknown | — | — | — | 1.74 |
| No. 0 | unknown | — | — | — | 0.74 |
| No. 0 | unknown | — | — | — | 0.76 |
Reference
Frequently Asked Questions
Common questions about Al2O4, answered from cross-validated data.
What is the band gap of Al2O4?
Al2O4 has a DFT-computed band gap of 0.14–1.10 eV across 24 reported structures.
More questions
Is Al2O4 a metal, semiconductor, or insulator?
With a band gap up to 1.10 eV it is a semiconductor.
Is Al2O4 thermodynamically stable?
Al2O4 has a lowest energy above hull of 0.184 eV/atom (above hull).
What is the crystal structure of Al2O4?
The lowest-energy reported polymorph of Al2O4 is orthorhombic symmetry, space group Pnnm (No. 58).
What is the density of Al2O4?
The computed density of the ground-state structure of Al2O4 is 3.62 g/cm³.
How many polymorphs of Al2O4 are known?
24 structures of Al2O4 are reported across 3 databases, spanning 4 distinct space groups.
What elements does Al2O4 contain?
Al2O4 contains Al and O (2 elements).
Where does the data for Al2O4 come from?
Al2O4 data is cross-referenced from materials_project, cod, omat24.
Explore
Related Compounds
Other Spinel Oxide Catalysts in the database.
Data sources & attribution
- materials_project — Data from the Materials Project. Cite: Jain et al., APL Materials 1, 011002 (2013).
- cod — Data from the Crystallography Open Database. Cite: Grazulis et al., Nucleic Acids Res. 40, D420 (2012).
- omat24 — Data from OMat24 (Meta FAIR). Cite: Barroso-Luque et al., arXiv 2410.12771 (2024).
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