AlCr2
AlCr2 is a metallic aluminum-chromium intermetallic compound that is frequently studied for its complex structural properties despite being thermodynamically unstable.
About AlCr2
AlCr2 is a metallic intermetallic compound composed of aluminum and chromium. Its electronic profile is defined by its metallic nature, lacking a band gap, which makes it a subject of interest for fundamental studies in alloy behavior and electron transport properties.
Despite its status as a thermodynamically unstable phase situated above the hull, this compound is notable for its significant data richness. It has been extensively documented across numerous structural databases, reflecting its importance in understanding the diverse phase space of aluminum-chromium systems.
Key Properties
Cross-validated computational properties for AlCr2, 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 AlCr2. 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 AlCr2, 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. |
|---|---|---|---|---|---|
| I4/mmm (No. 139) | tetragonal | 0.00 | 0.0000 | -0.128 | — |
| — | — | 0.00 | 0.0000 | -0.137 | — |
| I4/mmm (No. 139) | tetragonal | 0.00 | 0.1048 | -12.258 | 5.87 |
| Fmmm (No. 69) | orthorhombic | 0.00 | 0.1423 | -12.220 | 5.73 |
| — | — | 0.00 | 0.1447 | 0.008 | — |
| — | — | 0.00 | 0.1899 | 0.053 | — |
| — | — | 0.00 | 0.1932 | 0.056 | — |
| — | — | 0.00 | 0.2054 | 0.068 | — |
| — | — | 0.00 | 0.2074 | 0.070 | — |
| — | — | 0.00 | 0.2151 | 0.078 | — |
| — | — | 0.00 | 0.2151 | 0.078 | — |
| — | — | 0.00 | 0.2811 | 0.144 | — |
Synthesis Routes
Literature-extracted synthesis procedures targeting AlCr2.
Applications
Where AlCr2 is used.
Frequently Asked Questions
Common questions about AlCr2, answered from cross-validated data.
What is AlCr2?
AlCr2 is a metallic aluminum-chromium intermetallic compound that is frequently studied for its complex structural properties despite being thermodynamically unstable.
What is AlCr2 used for?
What is the band gap of AlCr2?
Is AlCr2 a metal, semiconductor, or insulator?
Is AlCr2 thermodynamically stable?
What is the crystal structure of AlCr2?
How many polymorphs of AlCr2 are known?
How is AlCr2 synthesized?
What elements does AlCr2 contain?
Where does the data for AlCr2 come from?
How It Compares
As a member of the aluminum-chromium binary system, AlCr2 represents a specific structural configuration that highlights the complexity of transition metal aluminides. While it does not share the stability of more common stoichiometric phases, its existence across many reported structures underscores its role as a critical data point for researchers mapping the stability limits of metallic alloys.
Data sources & attribution
- 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)
- materials_project — Data from the Materials Project (materialsproject.org). Cite: Jain et al., APL Materials 1, 011002 (2013). (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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