Ag2HgI4
silver mercury iodide · silver tetraiodomercurate
Silver mercury iodide is a semiconducting compound recognized for its thermodynamic stability and its characteristic thermochromic properties.
About silver mercury iodide
Silver mercury iodide is a distinct semiconducting compound that maintains thermodynamic stability within its structural phase space. Its complex lattice arrangement allows for notable ionic mobility, which is a defining characteristic of this material class.
Because of its electronic properties and structural versatility, this compound is primarily investigated for its role in thermochromic applications. It is frequently studied for its ability to undergo reversible color changes upon heating, making it a subject of interest in materials science research.
Key Properties
Cross-validated computational properties for silver mercury iodide, aggregated across 6 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 Ag2HgI4. 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 Ag2HgI4, 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. |
|---|---|---|---|---|---|
| — | — | 1.34 | 0.0000 | -0.388 | — |
| I-4 (No. 82) | tetragonal | 1.22 | 0.0000 | -2.240 | 5.75 |
| I-42m (No. 121) | tetragonal | 0.90 | 0.0000 | -0.207 | — |
| I-42m (No. 121) | tetragonal | 1.28 | 0.0011 | -2.239 | 5.75 |
| — | — | 1.20 | 0.0014 | -0.387 | — |
| P-42m (No. 111) | tetragonal | 1.10 | 0.0024 | -2.237 | 5.73 |
| — | — | 1.21 | 0.0024 | -0.386 | — |
| I-4 (No. 82) | tetragonal | 1.07 | 0.0143 | -0.193 | — |
| P-42m (No. 111) | tetragonal | 0.93 | 0.0185 | -0.189 | — |
| R3m (No. 160) | trigonal | 0.09 | 0.1250 | -2.115 | 1.26 |
| Cm (No. 8) | monoclinic | 0.00 | 0.1752 | -2.065 | 4.56 |
| P-42m (No. 111) | tetragonal | — | — | — | 5.65 |
Applications
Where silver mercury iodide is used.
Frequently Asked Questions
Common questions about silver mercury iodide, answered from cross-validated data.
What is Ag2HgI4?
Silver mercury iodide is a semiconducting compound recognized for its thermodynamic stability and its characteristic thermochromic properties.
What is Ag2HgI4 used for?
What is the band gap of Ag2HgI4?
Is Ag2HgI4 a metal, semiconductor, or insulator?
Is Ag2HgI4 thermodynamically stable?
How many polymorphs of Ag2HgI4 are known?
What elements does Ag2HgI4 contain?
Where does the data for Ag2HgI4 come from?
How It Compares
As a thermodynamically stable member of its class, this compound serves as a benchmark for ionic conductors that exhibit phase-dependent electronic behavior, distinguishing itself through its well-documented structural diversity.
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.
- cod — Data from the Crystallography Open Database (crystallography.net/cod/). Cite: Grazulis et al., J. Appl. Cryst. 42, 726 (2009). (CC0-1.0)
- nomad — Data from NOMAD (nomad-lab.eu). Cite: Draxl & Scheffler, J. Phys. Mater. 2, 036001 (2019). (CC-BY-4.0)
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