NpO2
neptunium dioxide · neptunium(IV) oxide
Neptunium dioxide is a stable actinide oxide widely studied for its role in nuclear science and fundamental actinide chemistry.
About neptunium dioxide
Neptunium dioxide is a key actinide compound that sits firmly on the convex hull, indicating its significant thermodynamic stability. As a metallic oxide, it serves as a critical subject for understanding the complex electronic behavior of transuranic materials under various conditions. Its structural versatility is evidenced by the extensive number of reported crystalline configurations found in scientific databases. This compound is essential for fundamental studies in actinide chemistry and the development of advanced nuclear fuel cycles, where its stability and behavior under irradiation are of primary concern to researchers. By providing a stable platform for investigating the electronic properties of neptunium, this material helps bridge the gap between theoretical models and practical applications in nuclear science.
Key Properties
Cross-validated computational properties for neptunium 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 NpO2. 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 NpO2, 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. |
|---|---|---|---|---|---|
| — | — | 7.99 | 0.0000 | -3.712 | — |
| Fm-3m (No. 225) | cubic | 0.00 | 0.0000 | -11.216 | 11.20 |
| Fm-3m (No. 225) | cubic | 0.00 | 0.0000 | -3.510 | — |
| — | — | 2.61 | 0.0017 | -3.710 | — |
| — | — | 2.48 | 0.1599 | -3.552 | — |
| — | — | 2.04 | 0.5843 | -3.128 | — |
| Cm (No. 8) | monoclinic | — | — | — | 7.66 |
| Cm (No. 8) | monoclinic | — | — | — | 5.53 |
| P1 (No. 1) | triclinic | — | — | — | 9.43 |
| C2 (No. 5) | monoclinic | — | — | — | 7.52 |
| Cm (No. 8) | monoclinic | — | — | — | 9.35 |
| Cm (No. 8) | monoclinic | — | — | — | 9.35 |
Applications
Where neptunium dioxide is used.
Patent Landscape
1 patent reference NpO2 or close compositional variants.
| Patent | Title | Assignee | Granted |
|---|---|---|---|
| 4686019 | Dissolution of PuO.sub.2 or NpO.sub.2 using electrolytically regenerated reagents | — | — |
Frequently Asked Questions
Common questions about neptunium dioxide, answered from cross-validated data.
What is NpO2?
Neptunium dioxide is a stable actinide oxide widely studied for its role in nuclear science and fundamental actinide chemistry.
What is NpO2 used for?
What is the band gap of NpO2?
Is NpO2 a metal, semiconductor, or insulator?
Is NpO2 thermodynamically stable?
What is the crystal structure of NpO2?
What is the density of NpO2?
How many polymorphs of NpO2 are known?
What elements does NpO2 contain?
Where does the data for NpO2 come from?
How It Compares
As a primary actinide oxide, NpO2 serves as a foundational reference point for the study of transuranic materials, representing a stable and well-characterized structure that informs our broader understanding of how heavy elements interact with oxygen in metallic-like electronic environments.
Data sources & attribution
- 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)
- 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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