Cs2I
Cs2I has a DFT band gap of 0.20 eV across 42 reported structures in 8 space groups. Cross-validated across 2 computational databases.
Key Properties
Cross-validated computational properties for Cs2I, aggregated across 2 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 Cs2I. Tight agreement means computed properties can be trusted without re-running calculations.
Only 1 independent DFT source (oqmd) reports a hull energy for Cs2I, so cross-source agreement can't be assessed yet.
Reported Structures
Lowest-energy structures reported for Cs2I, 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. |
|---|---|---|---|---|---|
| — | — | 0.00 | 0.0752 | -1.026 | — |
| — | — | 0.20 | 0.2560 | -0.845 | — |
| — | — | 0.20 | 0.4609 | -0.641 | — |
| P1 (No. 1) | triclinic | — | — | — | 2.87 |
| P1 (No. 1) | triclinic | — | — | — | 3.70 |
| P-1 (No. 2) | triclinic | — | — | — | 1.99 |
| P-1 (No. 2) | triclinic | — | — | — | 2.77 |
| P-1 (No. 2) | triclinic | — | — | — | 2.81 |
| P-1 (No. 2) | triclinic | — | — | — | 2.35 |
| P-1 (No. 2) | triclinic | — | — | — | 1.89 |
| P-1 (No. 2) | triclinic | — | — | — | 2.47 |
| P-1 (No. 2) | triclinic | — | — | — | 2.55 |
Frequently Asked Questions
Common questions about Cs2I, answered from cross-validated data.
What is the band gap of Cs2I?
Cs2I has a DFT-computed band gap of 0.20 eV across 42 reported structures. Standard DFT underestimates band gaps, so the measured gap is typically larger.
Is Cs2I a metal, semiconductor, or insulator?
Is Cs2I thermodynamically stable?
How many polymorphs of Cs2I are known?
What elements does Cs2I contain?
Where does the data for Cs2I come from?
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)
- mpaloe — Data from MP-ALOE. Cite: Kuner et al., npj Comput. Mater. (2025), doi:10.1038/s41524-025-01834-9.
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