CI2
CI2 is a metastable, semiconducting compound composed of carbon and iodine that is primarily studied for its complex structural diversity.
About CI2
CI2 is a binary carbon-iodine compound that exhibits semiconducting electronic properties. Its structural landscape is notably diverse, with numerous reported configurations across multiple databases, reflecting significant interest in its potential chemical behavior despite its complex synthesis requirements.
Because this material is found above the thermodynamic hull, it is considered inherently unstable under ambient conditions. This high-energy state makes it a subject of intense investigation for researchers looking to understand metastable phases and the fundamental limits of carbon-halogen bonding.
Key Properties
Cross-validated computational properties for CI2, aggregated across 6 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 CI2. 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 CI2, 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. |
|---|---|---|---|---|---|
| P21/c (No. 14) | monoclinic | 2.58 | 0.2902 | -3.803 | 3.55 |
| Pmm2 (No. 25) | orthorhombic | 0.00 | 1.3551 | 1.354 | — |
| — | — | 1.42 | 1.4014 | 1.396 | — |
| — | — | 1.33 | 1.4014 | 1.396 | — |
| — | — | 0.00 | 1.4088 | 1.404 | — |
| — | — | 0.00 | 2.9225 | 2.918 | — |
| P1 (No. 1) | triclinic | — | — | — | 8.73 |
| P1 (No. 1) | triclinic | — | — | — | 4.14 |
| P1 (No. 1) | triclinic | — | — | — | 4.52 |
| P1 (No. 1) | triclinic | — | — | — | 4.46 |
| P1 (No. 1) | triclinic | — | — | — | 8.64 |
| P1 (No. 1) | triclinic | — | — | — | 3.96 |
Applications
Where CI2 is used.
Frequently Asked Questions
Common questions about CI2, answered from cross-validated data.
What is CI2?
CI2 is a metastable, semiconducting compound composed of carbon and iodine that is primarily studied for its complex structural diversity.
What is CI2 used for?
What is the band gap of CI2?
Is CI2 a metal, semiconductor, or insulator?
Is CI2 thermodynamically stable?
What is the crystal structure of CI2?
What is the density of CI2?
How many polymorphs of CI2 are known?
What elements does CI2 contain?
Where does the data for CI2 come from?
How It Compares
As a unique binary system, CI2 serves as a specialized case study within the broader field of carbon halides. Unlike more common and stable halogenated carbon compounds, its position relative to the thermodynamic hull highlights the challenges in stabilizing this specific stoichiometry, setting it apart as a distinct example of a metastable semiconducting material.
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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