Fe8O9
Fe8O9 is a metastable semiconducting iron oxide being investigated as a high-capacity conversion anode for electrochemical energy storage devices.
About Fe8O9
Fe8O9 is a semiconducting conversion oxide that exists in a metastable state. As a member of the iron-oxygen system, it represents a complex structural arrangement that distinguishes it from simpler binary iron oxides. Its electronic character and structural configuration make it an intriguing subject for research into high-capacity anode materials for next-generation batteries. The material is characterized by a diverse set of reported structures, highlighting its intricate phase space. Researchers study this compound to understand how metastable oxides can facilitate reversible electrochemical reactions. By leveraging conversion mechanisms, it aims to overcome the capacity limitations of traditional intercalation-based electrode materials.
Key Properties
Cross-validated computational properties for Fe8O9, 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.
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 Fe8O9. 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 Fe8O9, 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 | 1.20 | 0.0486 | -8.105 | 5.30 |
| P-1 (No. 2) | triclinic | 1.41 | 0.0613 | -8.092 | 5.33 |
| P-1 (No. 2) | triclinic | 0.00 | 0.1651 | -1.114 | — |
| P-1 (No. 2) | triclinic | — | — | — | 6.03 |
| P-1 (No. 2) | triclinic | — | — | — | 5.33 |
| P-1 (No. 2) | triclinic | — | — | — | 5.79 |
Applications
Where Fe8O9 is used.
Frequently Asked Questions
Common questions about Fe8O9, answered from cross-validated data.
What is Fe8O9?
Fe8O9 is a metastable semiconducting iron oxide being investigated as a high-capacity conversion anode for electrochemical energy storage devices.
What is Fe8O9 used for?
What is the band gap of Fe8O9?
Is Fe8O9 a metal, semiconductor, or insulator?
Is Fe8O9 thermodynamically stable?
What is the crystal structure of Fe8O9?
What is the density of Fe8O9?
How many polymorphs of Fe8O9 are known?
What elements does Fe8O9 contain?
Where does the data for Fe8O9 come from?
How It Compares
Within the conversion oxide anodes class.
Within the class of conversion oxide anodes, Fe8O9 occupies a unique niche compared to more common binary oxides like Fe2O3 or Fe3O4. While those materials are well-established, Fe8O9 represents a more complex, metastable stoichiometry that offers a different pathway for ion storage and structural evolution during electrochemical cycling.
Related Compounds
Other Conversion Oxide Anodes in the database.
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)
- mpaloe — Data from MP-ALOE. Cite: Kuner et al., npj Comput. Mater. (2025), doi:10.1038/s41524-025-01834-9.
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