HgCl
mercury(I) chloride · calomel
HgCl is a stable, semiconducting mercury halide that has been extensively studied for its structural diversity and chemical properties.
About mercury(I) chloride
HgCl is a well-characterized inorganic compound that exists as a thermodynamically stable phase on the convex hull. Its electronic structure exhibits semiconducting behavior, making it a subject of interest in fundamental materials research and historical chemical studies. With a vast array of reported structures, it remains one of the most structurally documented mercury-based materials in scientific databases. The compound is valued for its specific physical properties and its role as a precursor in various chemical applications. Its stability and predictable electronic character provide a reliable foundation for understanding mercury-halogen bonding dynamics in solid-state systems.
Key Properties
Cross-validated computational properties for mercury(I) chloride, 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 HgCl. 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 HgCl, 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 | 2.74 | 0.0000 | -1.926 | 6.92 |
| — | — | 2.51 | 0.0000 | -0.695 | — |
| I4/mmm (No. 139) | tetragonal | 2.25 | 0.0000 | -0.400 | — |
| I4/mmm (No. 139) | tetragonal | 0.00 | 0.2412 | -0.159 | — |
| P4/mmm (No. 123) | tetragonal | 0.00 | 0.2929 | -0.107 | — |
| — | — | 0.00 | 0.3331 | -0.362 | — |
| — | — | 0.00 | 0.3389 | -0.356 | — |
| Pmmm (No. 47) | orthorhombic | 0.00 | 0.3482 | -0.052 | — |
| — | — | 0.00 | 0.3788 | -0.316 | — |
| P4/mmm (No. 123) | tetragonal | 0.00 | 0.3877 | -0.012 | — |
| — | — | 0.00 | 0.3924 | -0.303 | — |
| — | — | 0.00 | 0.4713 | -0.224 | — |
Applications
Where mercury(I) chloride is used.
Frequently Asked Questions
Common questions about mercury(I) chloride, answered from cross-validated data.
What is HgCl?
HgCl is a stable, semiconducting mercury halide that has been extensively studied for its structural diversity and chemical properties.
What is HgCl used for?
What is the band gap of HgCl?
Is HgCl a metal, semiconductor, or insulator?
Is HgCl thermodynamically stable?
What is the crystal structure of HgCl?
What is the density of HgCl?
How many polymorphs of HgCl are known?
What elements does HgCl contain?
Where does the data for HgCl come from?
How It Compares
As a standalone representative of its chemical class in this context, HgCl serves as a benchmark for mercury-based halides. Its status as a thermodynamically stable semiconductor distinguishes it from more volatile or unstable mercury species, positioning it as a robust material for comparative studies in halide chemistry.
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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