Ca2O9S2
Ca2O9S2 has a DFT band gap of 0.02–1.07 eV across 5 reported structures in 4 space groups; its reference structure is trigonal (P31 (No. 144)). Cross-validated across 2 computational databases.
Key Properties
Cross-validated computational properties for Ca2O9S2, 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 Ca2O9S2. Tight agreement means computed properties can be trusted without re-running calculations.
Only 1 independent DFT source (materials_project) reports a hull energy for Ca2O9S2, so cross-source agreement can't be assessed yet.
Reported Structures
Lowest-energy structures reported for Ca2O9S2, 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. |
|---|---|---|---|---|---|
| P32 (No. 145) | trigonal | 1.07 | 0.1694 | -6.665 | 2.62 |
| P31 (No. 144) | trigonal | 0.93 | 0.1698 | -6.664 | 2.60 |
| C2 (No. 5) | monoclinic | 0.02 | 0.1699 | -6.664 | 2.61 |
| P3121 (No. 152) | trigonal | 0.83 | 0.1716 | -6.663 | 2.61 |
| P31 (No. 144) | trigonal | — | — | — | 2.71 |
Frequently Asked Questions
Common questions about Ca2O9S2, answered from cross-validated data.
What is the band gap of Ca2O9S2?
Ca2O9S2 has a DFT-computed band gap of 0.02–1.07 eV across 5 reported structures. Standard DFT underestimates band gaps, so the measured gap is typically larger.
Is Ca2O9S2 a metal, semiconductor, or insulator?
Is Ca2O9S2 thermodynamically stable?
What is the crystal structure of Ca2O9S2?
What is the density of Ca2O9S2?
How many polymorphs of Ca2O9S2 are known?
What elements does Ca2O9S2 contain?
Where does the data for Ca2O9S2 come from?
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)
- cod — Data from the Crystallography Open Database (crystallography.net/cod/). Cite: Grazulis et al., J. Appl. Cryst. 42, 726 (2009). (CC0-1.0)
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