NaI
Sodium iodide · NaI
Sodium iodide is a stable, insulating salt primarily used for its ability to detect ionizing radiation.
About Sodium iodide
Sodium iodide is a thermodynamically stable inorganic salt that functions as a wide-band-gap insulator. Its electronic structure is characterized by a significant energy gap that prevents electrical conduction under standard conditions, making it an ideal candidate for optical and radiation-detection applications.
Due to its high structural reliability and well-documented physical properties, this compound is a cornerstone in the field of radiation physics. It is frequently utilized in devices that require the conversion of high-energy particles into detectable light pulses, serving as a critical component in diagnostic equipment.
Key Properties
Cross-validated computational properties for Sodium iodide, aggregated across 3 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 NaI. 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 NaI, 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. |
|---|---|---|---|---|---|
| P63/mmc (No. 194) | hexagonal | 3.60 | 0.0000 | -1.367 | — |
| Fm-3m (No. 225) | cubic | 3.57 | 0.0000 | -2.883 | 3.73 |
| — | — | 3.76 | 0.0005 | -1.416 | — |
| — | — | 3.78 | 0.0016 | -1.415 | — |
| — | — | 3.77 | 0.0086 | -1.408 | — |
| — | — | 3.71 | 0.0087 | -1.408 | — |
| Fm-3m (No. 225) | cubic | 3.85 | 0.0090 | -1.358 | — |
| — | — | 3.75 | 0.0163 | -1.400 | — |
| — | — | 4.01 | 0.0492 | -1.367 | — |
| — | — | 3.98 | 0.0500 | -1.367 | — |
| — | — | 4.02 | 0.0520 | -1.365 | — |
| — | — | 3.42 | 0.0537 | -1.363 | — |
Applications
Where Sodium iodide is used.
Frequently Asked Questions
Common questions about Sodium iodide, answered from cross-validated data.
What is NaI?
Sodium iodide is a stable, insulating salt primarily used for its ability to detect ionizing radiation.
What is NaI used for?
What is the band gap of NaI?
Is NaI a metal, semiconductor, or insulator?
Is NaI thermodynamically stable?
What is the crystal structure of NaI?
How many polymorphs of NaI are known?
What elements does NaI contain?
Where does the data for NaI come from?
How It Compares
As a fundamental halide, sodium iodide occupies a central role in the study of alkali metal salts. It is recognized for its high degree of structural stability and is one of the most frequently characterized materials in its class, serving as a benchmark for performance in scintillation technology.
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.
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