NO2
nitrogen dioxide · NO2
Nitrogen dioxide is a thermodynamically stable, semiconducting oxide of nitrogen that plays a key role in atmospheric chemistry and industrial processes.
About nitrogen dioxide
Nitrogen dioxide is a prominent nitrogen oxide that exists as a semiconducting molecule. Its thermodynamic stability on the convex hull makes it a significant subject of study in both fundamental chemistry and atmospheric science. The compound is characterized by its distinct reactivity and role as a critical intermediate in various industrial and environmental processes. Given its structural diversity, it is frequently investigated across multiple experimental and computational databases to better understand its molecular behavior. This compound serves as a vital component in the study of nitrogen-based species, providing insights into gas-phase kinetics and oxidation mechanisms. Its presence is widely monitored due to its role in atmospheric cycles and its impact on air quality, marking it as a highly relevant species in chemical research.
Key Properties
Cross-validated computational properties for nitrogen dioxide, 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 NO2. 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 NO2, 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. |
|---|---|---|---|---|---|
| Im-3 (No. 204) | cubic | 2.83 | 0.0000 | -6.764 | 2.00 |
| Im-3 (No. 204) | cubic | 2.78 | 0.0000 | -0.184 | — |
| — | — | 2.48 | 0.0000 | -0.507 | — |
| P21/c (No. 14) | monoclinic | 2.52 | 0.0010 | -0.182 | — |
| P21/c (No. 14) | monoclinic | 2.70 | 0.0015 | -6.762 | 1.99 |
| — | — | 2.73 | 0.0051 | -0.501 | — |
| Im-3 (No. 204) | cubic | 2.85 | 0.0268 | -6.737 | 1.46 |
| — | — | 2.72 | 0.0433 | -0.463 | — |
| Im-3 (No. 204) | cubic | 2.88 | 0.0438 | -0.140 | — |
| P21/m (No. 11) | monoclinic | 1.57 | 0.0801 | -0.103 | — |
| — | — | 1.70 | 0.1286 | -0.378 | — |
| P1 (No. 1) | triclinic | 0.00 | 0.1587 | -0.025 | — |
Applications
Where nitrogen dioxide is used.
Patent Landscape
43 patents reference NO2 or close compositional variants.
| Patent | Title | Assignee | Granted |
|---|---|---|---|
| 9408994 | Conversion of nitrogen dioxide (NO2) to nitric oxide (NO) | — | — |
| 8083997 | Conversion of nitrogen dioxide (NO2) to nitric oxide (NO) | — | — |
| 11202880 | Conversion of nitrogen dioxide (NO2) to nitric oxide (NO) | — | — |
| 11324912 | Systems and methods for indicating lifetime of an NO2-to-NO reactor cartridge used to deliver NO for inhalatio | — | — |
| 7947227 | Kit for the conversion of nitrogen dioxide (NO2) to nitric oxide (NO) | — | — |
| 11291793 | Conversion of nitrogen dioxide (NO2) to nitric oxide (NO) | — | — |
| 9458022 | Process and apparatus for separating NO2 from a CO2 and NO2—containing fluid | — | — |
| 12059661 | Conversion of nitrogen dioxide (NO2) to nitric oxide (NO) | — | — |
| 10124142 | Conversion of nitrogen dioxide (NO2) to nitric oxide (NO) | — | — |
| 10086352 | Conversion of nitrogen dioxide (NO2) to nitric oxide (NO) | — | — |
Frequently Asked Questions
Common questions about nitrogen dioxide, answered from cross-validated data.
What is NO2?
Nitrogen dioxide is a thermodynamically stable, semiconducting oxide of nitrogen that plays a key role in atmospheric chemistry and industrial processes.
What is NO2 used for?
What is the band gap of NO2?
Is NO2 a metal, semiconductor, or insulator?
Is NO2 thermodynamically stable?
What is the crystal structure of NO2?
What is the density of NO2?
How many polymorphs of NO2 are known?
What elements does NO2 contain?
Where does the data for NO2 come from?
How It Compares
As a fundamental nitrogen oxide, nitrogen dioxide holds a unique position in chemical research, serving as a primary reference point for understanding the behavior of small, stable nitrogen-oxygen species in various environmental and industrial contexts.
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.
- 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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