Tl
thallium · element 81
Thallium is a soft, heavy, and thermodynamically stable metallic element known for its complex structural behavior and specialized industrial utility.
About thallium
Thallium is a soft, heavy post-transition metal that exists as a thermodynamically stable phase. Its metallic character and structural versatility are evidenced by the numerous crystalline forms documented across scientific databases, reflecting its complex behavior in the solid state.
As a distinct elemental material, thallium is valued for its specific physical properties, though its use is strictly regulated due to its toxicity. It remains a subject of fundamental interest in materials science for its role in developing advanced optical components and specialized alloys.
Key Properties
Cross-validated computational properties for thallium, 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 Tl. 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 Tl, 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 | 0.00 | 0.0000 | 0.000 | — |
| P63/mmc (No. 194) | hexagonal | 0.00 | 0.0000 | -53.179 | 11.35 |
| Fm-3m (No. 225) | cubic | 0.00 | 0.0000 | 0.011 | — |
| I4/mmm (No. 139) | tetragonal | 0.00 | 0.0000 | 0.019 | — |
| P63/mmc (No. 194) | hexagonal | 0.00 | 0.0000 | 0.017 | — |
| R-3m (No. 166) | trigonal | 0.00 | 0.0000 | 0.012 | — |
| Im-3m (No. 229) | cubic | 0.00 | 0.0000 | 0.004 | — |
| P63/mmc (No. 194) | hexagonal | 0.00 | 0.0000 | 0.000 | — |
| I-43m (No. 217) | cubic | 0.00 | 0.0000 | 0.006 | — |
| Im-3m (No. 229) | cubic | 0.00 | 0.0000 | 0.004 | — |
| I4/mmm (No. 139) | tetragonal | 0.00 | 0.0000 | 0.019 | — |
| — | — | 0.00 | 0.0000 | 0.000 | — |
Applications
Where thallium is used.
Frequently Asked Questions
Common questions about thallium, answered from cross-validated data.
What is Tl?
Thallium is a soft, heavy, and thermodynamically stable metallic element known for its complex structural behavior and specialized industrial utility.
What is Tl used for?
What is the band gap of Tl?
Is Tl a metal, semiconductor, or insulator?
Is Tl thermodynamically stable?
What is the crystal structure of Tl?
How many polymorphs of Tl are known?
What elements does Tl contain?
Where does the data for Tl come from?
How It Compares
As a pure elemental metal, thallium occupies a unique position in materials science, serving as a foundational reference point for heavy metal chemistry rather than acting as a member of a broader compound class.
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)
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