Al2O
Al2O is a metallic aluminum suboxide that exists as a metastable phase with high structural complexity.
About Al2O
Al2O is an aluminum suboxide that exhibits metallic electronic character, distinguishing it from the typical insulating behavior found in many related aluminum-based oxides. Due to its position above the thermodynamic stability hull, it is considered a metastable phase that requires specific synthetic conditions to access.
Despite its instability, this compound is of significant interest in materials science due to its structural diversity, with hundreds of reported configurations. It serves as a unique subject for researchers investigating non-stoichiometric oxide behavior and the potential for metallic phases in catalytic applications.
Key Properties
Cross-validated computational properties for Al2O, 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 Al2O. 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 Al2O, 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. |
|---|---|---|---|---|---|
| P1 (No. 1) | triclinic | 0.00 | 0.1835 | -5.866 | 1.52 |
| P1 (No. 1) | triclinic | 0.00 | 0.1836 | -5.866 | 1.51 |
| Pm (No. 6) | monoclinic | 0.00 | 0.5401 | -1.301 | — |
| Pmmm (No. 47) | orthorhombic | 0.00 | 0.7132 | -1.128 | — |
| — | — | 0.00 | 0.9601 | -0.854 | — |
| P6/mmm (No. 191) | hexagonal | 0.00 | 1.7465 | -0.094 | — |
| Fm-3m (No. 225) | cubic | 0.00 | 1.7621 | -4.288 | 2.52 |
| — | — | 0.00 | 1.7659 | -0.048 | — |
| Fm-3m (No. 225) | cubic | 0.00 | 1.7868 | -0.054 | — |
| — | — | 0.00 | 2.2319 | 0.418 | — |
| P1 (No. 1) | triclinic | — | — | — | 2.24 |
| P1 (No. 1) | triclinic | — | — | — | 2.10 |
Applications
Where Al2O is used.
Patent Landscape
1 patent reference Al2O or close compositional variants.
| Patent | Title | Assignee | Granted |
|---|---|---|---|
| 6849101 | Method using selected carbons to react with Al2O and Al vapors in the carbothermic production of aluminum | — | — |
Frequently Asked Questions
Common questions about Al2O, answered from cross-validated data.
What is Al2O?
Al2O is a metallic aluminum suboxide that exists as a metastable phase with high structural complexity.
What is Al2O used for?
What is the band gap of Al2O?
Is Al2O a metal, semiconductor, or insulator?
Is Al2O thermodynamically stable?
What is the crystal structure of Al2O?
What is the density of Al2O?
How many polymorphs of Al2O are known?
What elements does Al2O contain?
Where does the data for Al2O come from?
How It Compares
Unlike the highly stable and widely utilized MgAl2O4 spinel or the insulating Al2O3, Al2O is characterized by its metallic nature and inherent thermodynamic instability. While siblings like LaMnO3 and LaNiO3 are often explored for their complex magnetic and conductive properties in perovskite-like frameworks, Al2O represents a more unconventional, transient entry within the broader landscape of oxide catalysts.
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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