CaSO4
calcium sulfate · anhydrite
Calcium sulfate is a stable, insulating mineral compound widely utilized in construction materials and industrial manufacturing.
About calcium sulfate
Calcium sulfate is a thermodynamically stable inorganic compound that exists in a wide-gap insulating state. Its structural versatility is evidenced by the numerous distinct crystalline arrangements documented across major materials databases, reflecting its complex behavior under varying conditions. This compound serves as a fundamental material in industrial applications, valued for its chemical stability and abundance. Its ability to transition between hydrated and anhydrous forms makes it a critical component in building materials and chemical processing.
Key Properties
Cross-validated computational properties for calcium sulfate, 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 CaSO4. 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 CaSO4, 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. |
|---|---|---|---|---|---|
| Cmcm (No. 63) | orthorhombic | 6.47 | 0.0000 | -2.328 | — |
| — | — | 6.33 | 0.0000 | -2.539 | — |
| Cmcm (No. 63) | orthorhombic | 5.95 | 0.0000 | -6.991 | 2.98 |
| — | — | 6.05 | 0.0012 | -2.537 | — |
| — | — | 5.95 | 0.0026 | -2.536 | — |
| P21/c (No. 14) | monoclinic | 6.56 | 0.0087 | -2.319 | — |
| P6222 (No. 180) | hexagonal | 5.68 | 0.0120 | -6.979 | 2.57 |
| P6422 (No. 181) | hexagonal | 5.69 | 0.0127 | -6.979 | 2.56 |
| P21/c (No. 14) | monoclinic | 5.97 | 0.0135 | -6.978 | 3.19 |
| — | — | 6.22 | 0.0215 | -2.517 | — |
| P6222 (No. 180) | hexagonal | 5.83 | 0.0284 | -2.300 | — |
| — | — | 6.56 | 0.0342 | -2.504 | — |
Synthesis Routes
Literature-extracted synthesis procedures targeting CaSO4.
Applications
Where calcium sulfate is used.
Patent Landscape
2 patents reference CaSO4 or close compositional variants.
| Patent | Title | Assignee | Granted |
|---|---|---|---|
| 11535911 | Method for reducing formation of CaSO4 and Fe2O3 containing deposits in a pressure oxidation autoclave and/or | — | — |
| 4610861 | Process for metal recovery by solvent extraction from CaSO.sub.4 containing sulfate solutions | — | — |
Frequently Asked Questions
Common questions about calcium sulfate, answered from cross-validated data.
What is CaSO4?
Calcium sulfate is a stable, insulating mineral compound widely utilized in construction materials and industrial manufacturing.
What is CaSO4 used for?
What is the band gap of CaSO4?
Is CaSO4 a metal, semiconductor, or insulator?
Is CaSO4 thermodynamically stable?
What is the crystal structure of CaSO4?
How many polymorphs of CaSO4 are known?
How is CaSO4 synthesized?
What elements does CaSO4 contain?
Where does the data for CaSO4 come from?
How It Compares
As a highly stable and well-documented material, calcium sulfate stands as a benchmark for inorganic sulfates, representing a standard for structural complexity and thermodynamic reliability within its chemical family.
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)
- 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)
- 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)
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