CO
Carbon monoxide · Carbon oxide, Monocarbon monoxide
Carbon monoxide is a simple, highly reactive diatomic molecule that serves as a vital chemical intermediate and ligand in various industrial and laboratory applications.
About Carbon monoxide
Carbon monoxide is a fundamental diatomic molecule consisting of a carbon atom triple-bonded to an oxygen atom. Despite its simple composition, it exhibits a wide-band-gap insulating character that distinguishes its electronic behavior from more complex metallic or semiconducting oxides. Its thermodynamic profile indicates it exists above the hull, reflecting its high reactivity and tendency to participate in chemical transformations rather than remaining in a static solid state. Given its extensive documentation across multiple structural databases, it remains a heavily scrutinized subject in fundamental chemical research. Its significance lies in its role as a versatile ligand in coordination chemistry and a critical precursor in industrial synthetic processes. The compound serves as a cornerstone for understanding bonding dynamics and molecular interactions in gas-phase and surface-adsorbed systems.
Key Properties
Cross-validated computational properties for Carbon monoxide, 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 CO. 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 CO, 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. |
|---|---|---|---|---|---|
| C2/m (No. 12) | monoclinic | 0.99 | 0.5260 | -0.463 | — |
| Pnma (No. 62) | orthorhombic | 0.00 | 0.5494 | -7.867 | 2.17 |
| P4/nmm (No. 129) | tetragonal | 4.57 | 0.6112 | -0.378 | — |
| P213 (No. 198) | cubic | 5.81 | 0.6238 | -0.365 | — |
| R3c (No. 161) | trigonal | 6.02 | 0.6292 | -0.360 | — |
| P213 (No. 198) | cubic | 6.15 | 0.6618 | -7.754 | 0.88 |
| P212121 (No. 19) | orthorhombic | 5.95 | 0.6698 | -7.746 | 0.89 |
| R3c (No. 161) | trigonal | 5.85 | 0.6773 | -7.739 | 1.03 |
| — | — | 5.22 | 0.7398 | -0.415 | — |
| P-6m2 (No. 187) | hexagonal | 0.00 | 2.7944 | 1.805 | — |
| P4/mmm (No. 123) | tetragonal | 0.00 | 3.0375 | 2.048 | — |
| — | — | 0.00 | 3.2353 | 2.080 | — |
Applications
Where Carbon monoxide is used.
Frequently Asked Questions
Common questions about Carbon monoxide, answered from cross-validated data.
What is CO?
Carbon monoxide is a simple, highly reactive diatomic molecule that serves as a vital chemical intermediate and ligand in various industrial and laboratory applications.
What is CO used for?
What is the band gap of CO?
Is CO a metal, semiconductor, or insulator?
Is CO thermodynamically stable?
What is the crystal structure of CO?
How many polymorphs of CO are known?
What elements does CO contain?
Where does the data for CO come from?
How It Compares
As a unique diatomic species, carbon monoxide occupies a distinct position in materials science where it serves as a primary reference point for molecular bonding and coordination chemistry, rather than functioning as a traditional bulk solid-state material.
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)
- 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)
- mpaloe — Data from MP-ALOE. Cite: Kuner et al., npj Comput. Mater. (2025), doi:10.1038/s41524-025-01834-9.
- nomad — Data from NOMAD (nomad-lab.eu). Cite: Draxl & Scheffler, J. Phys. Mater. 2, 036001 (2019). (CC-BY-4.0)
- cod — Data from the Crystallography Open Database (crystallography.net/cod/). Cite: Grazulis et al., J. Appl. Cryst. 42, 726 (2009). (CC0-1.0)
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