AlO2
AlO2 is a semiconducting aluminum oxide compound categorized within the spinel-related catalyst class that exhibits significant thermodynamic instability.
About AlO2
AlO2 is a semiconducting oxide that exists as a complex member of the spinel-related catalyst family. Despite its classification, it is characterized by thermodynamic instability, typically appearing above the hull in computational phase diagrams. This suggests that while it is a subject of significant structural interest, it may be difficult to synthesize or maintain in a stable crystalline form under standard conditions.
Its presence in extensive structural databases highlights its role in theoretical investigations of aluminum-oxygen systems. Researchers study this compound to understand the limits of spinel-type architectures and the electronic behavior of non-stoichiometric aluminum oxides in catalytic environments.
Key Properties
Cross-validated computational properties for AlO2, aggregated across 5 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.
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.
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.
StructuresCount of reported calculated crystal structures for this formula, including alternate polymorphs, source databases, and observed space groups.
Cross-Source DFT Agreement
How well independent DFT databases agree on the thermodynamics of AlO2. Tight agreement means computed properties can be trusted without re-running calculations.
Agreement ScoreA normalized confidence score summarizing how closely independent DFT databases agree. Higher scores mean tighter cross-source agreement.
Hull SpreadDifference between the highest and lowest energy-above-hull values reported by comparable sources. Smaller spread means less thermodynamic disagreement.
Sources ComparedNumber and names of computational sources with comparable entries for this formula.
Space Group ConsensusWhether independent sources predict the same crystal symmetry for the lowest-energy structure.
Reported Structures
Lowest-energy structures reported for AlO2, 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 |
| Pnnm (No. 58) | orthorhombic | 0.27 | 0.2647 | -2.498 | — |
| Cmcm (No. 63) | orthorhombic | 0.00 | 0.2953 | -7.107 | 3.34 |
| — | — | 0.00 | 0.3327 | -2.388 | — |
| Cmcm (No. 63) | orthorhombic | 0.00 | 0.3559 | -7.047 | 3.19 |
| Cmcm (No. 63) | orthorhombic | 0.00 | 0.3977 | -2.365 | — |
| Pnma (No. 62) | orthorhombic | 1.08 | 0.4353 | -6.967 | 2.95 |
| — | — | 0.00 | 0.4627 | -2.258 | — |
| — | — | 0.00 | 0.5527 | -2.168 | — |
| P2/m (No. 10) | monoclinic | 0.00 | 1.0631 | -1.700 | — |
| P6/mmm (No. 191) | hexagonal | 0.00 | 1.8048 | -0.958 | — |
Synthesis Routes
Literature-extracted synthesis procedures targeting AlO2.
Applications
Where AlO2 is used.
Frequently Asked Questions
Common questions about AlO2, answered from cross-validated data.
What is AlO2?
AlO2 is a semiconducting aluminum oxide compound categorized within the spinel-related catalyst class that exhibits significant thermodynamic instability.
What is AlO2 used for?
What is the band gap of AlO2?
Is AlO2 a metal, semiconductor, or insulator?
Is AlO2 thermodynamically stable?
What is the crystal structure of AlO2?
What is the density of AlO2?
How many polymorphs of AlO2 are known?
How is AlO2 synthesized?
What elements does AlO2 contain?
Where does the data for AlO2 come from?
How It Compares
Unlike the highly stable and widely utilized MgAl2O4 or the robust binary oxides like Al2O3, AlO2 is notably less thermodynamically favorable. While members such as LaMnO3 and LaNiO3 are prized for their predictable catalytic performance in complex oxide systems, AlO2 remains a more elusive and theoretically challenging material within the broader class of spinel-related oxides.
Data sources & attribution
- materials_project — Data from the Materials Project (materialsproject.org). Cite: Jain et al., APL Materials 1, 011002 (2013). (CC-BY-4.0)
- jarvis — Data from JARVIS (jarvis.nist.gov), NIST. Cite: Choudhary et al., npj Comp. Mater. 6, 173 (2020). (LicenseRef-US-Gov-PD)
- oqmd — Data from the OQMD (oqmd.org). Cite: Saal et al., JOM 65, 1501 (2013); Kirklin et al., npj Comp. Mater. 1, 15010 (2015). (CC-BY-4.0)
- mpaloe — Data from MP-ALOE. Cite: Kuner et al., npj Comput. Mater. (2025), doi:10.1038/s41524-025-01834-9.
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