HgI
mercury(I) iodide · mercurous iodide
HgI is a thermodynamically stable, semiconducting inorganic compound formed from mercury and iodine that exhibits a high degree of structural variety.
About mercury(I) iodide
HgI is a thermodynamically stable inorganic compound composed of mercury and iodine. As a semiconducting material, it occupies a unique position in the study of metal halides, characterized by its presence on the convex hull of stability which indicates a robust energetic state under standard conditions. The compound is notable for its significant structural diversity, with numerous reported crystalline arrangements documented across major materials databases. This structural richness makes it a subject of interest for researchers investigating the relationship between atomic configuration and electronic behavior in mercury-based systems.
Key Properties
Cross-validated computational properties for mercury(I) iodide, 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 HgI. 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 HgI, 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. |
|---|---|---|---|---|---|
| I4/mmm (No. 139) | tetragonal | 1.66 | 0.0000 | -1.360 | 7.19 |
| — | — | 1.40 | 0.0000 | -0.302 | — |
| I4/mmm (No. 139) | tetragonal | 1.48 | 0.0229 | -0.093 | — |
| Immm (No. 71) | orthorhombic | 0.00 | 0.1052 | -0.011 | — |
| — | — | 0.00 | 0.1651 | -0.137 | — |
| Pmmm (No. 47) | orthorhombic | 0.00 | 0.1772 | 0.061 | — |
| — | — | 0.00 | 0.2075 | -0.094 | — |
| P4/mmm (No. 123) | tetragonal | 0.00 | 0.2112 | 0.095 | — |
| — | — | 0.00 | 0.2466 | -0.055 | — |
| P4/mmm (No. 123) | tetragonal | 0.00 | 0.2693 | 0.153 | — |
| — | — | 0.00 | 0.2769 | -0.025 | — |
| — | — | 0.00 | 0.2939 | -0.008 | — |
Applications
Where mercury(I) iodide is used.
Frequently Asked Questions
Common questions about mercury(I) iodide, answered from cross-validated data.
What is HgI?
HgI is a thermodynamically stable, semiconducting inorganic compound formed from mercury and iodine that exhibits a high degree of structural variety.
What is HgI used for?
What is the band gap of HgI?
Is HgI a metal, semiconductor, or insulator?
Is HgI thermodynamically stable?
What is the crystal structure of HgI?
What is the density of HgI?
How many polymorphs of HgI are known?
What elements does HgI contain?
Where does the data for HgI come from?
How It Compares
As a distinct mercury-iodide phase, HgI serves as a foundational example of stable binary halides. Its ability to maintain thermodynamic stability while exhibiting semiconducting properties distinguishes it from less stable or metallic counterparts, positioning it as a key reference point for understanding the bonding and electronic trends within the broader family of mercury-based inorganic materials.
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)
- cod — Data from the Crystallography Open Database (crystallography.net/cod/). Cite: Grazulis et al., J. Appl. Cryst. 42, 726 (2009). (CC0-1.0)
- mpaloe — Data from MP-ALOE. Cite: Kuner et al., npj Comput. Mater. (2025), doi:10.1038/s41524-025-01834-9.
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