ClO
chlorine monoxide · chlorine radical
Chlorine monoxide is a reactive, unstable radical molecule that acts as a key intermediate in atmospheric ozone depletion processes.
About chlorine monoxide
Chlorine monoxide is a reactive radical species composed of chlorine and oxygen. As a semiconducting molecule, it plays a critical role in atmospheric chemistry, particularly in the catalytic cycles that influence the ozone layer. Its electronic structure is defined by an unpaired electron, which drives its high reactivity and short-lived existence in natural environments.
Due to its position above the thermodynamic hull, this compound is inherently unstable and tends to participate rapidly in chemical reactions rather than existing as a stable bulk solid. Its presence is primarily observed in transient states, making it a subject of extensive study in environmental science and atmospheric modeling.
Key Properties
Cross-validated computational properties for chlorine monoxide, aggregated across 4 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 ClO. 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 ClO, 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. |
|---|---|---|---|---|---|
| I41/amd (No. 141) | tetragonal | 1.69 | 0.2163 | -3.447 | 0.37 |
| — | — | 0.00 | 0.2211 | 0.014 | — |
| P1 (No. 1) | triclinic | 0.00 | 0.3203 | 0.314 | — |
| — | — | 0.00 | 0.7405 | 0.533 | — |
| I4/mmm (No. 139) | tetragonal | 0.00 | 0.8236 | 0.818 | — |
| P4/mmm (No. 123) | tetragonal | 0.00 | 0.8333 | 0.827 | — |
| — | — | 0.00 | 1.1083 | 0.901 | — |
| — | — | 0.00 | 1.1103 | 0.903 | — |
| P-6m2 (No. 187) | hexagonal | 0.00 | 1.1287 | 1.123 | — |
| — | — | 0.00 | 1.2737 | 1.066 | — |
| — | — | 0.00 | 1.2793 | 1.072 | — |
| P4mm (No. 99) | tetragonal | 0.00 | 1.3079 | 1.302 | — |
Applications
Where chlorine monoxide is used.
Frequently Asked Questions
Common questions about chlorine monoxide, answered from cross-validated data.
What is ClO?
Chlorine monoxide is a reactive, unstable radical molecule that acts as a key intermediate in atmospheric ozone depletion processes.
What is ClO used for?
What is the band gap of ClO?
Is ClO a metal, semiconductor, or insulator?
Is ClO thermodynamically stable?
What is the crystal structure of ClO?
How many polymorphs of ClO are known?
What elements does ClO contain?
Where does the data for ClO come from?
How It Compares
As a highly reactive radical, chlorine monoxide functions as a distinct chemical intermediate rather than a traditional structural material. Unlike stable, bulk inorganic compounds, it is defined by its fleeting existence and its pivotal role in gas-phase atmospheric kinetics.
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)
- 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)
- 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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