Na3AlF6
cryolite · sodium hexafluoroaluminate
Cryolite is a stable, insulating mineral compound primarily used as a flux to facilitate the electrolytic extraction of aluminum.
About cryolite
Cryolite is a naturally occurring fluoride mineral that serves as a cornerstone in metallurgical processes. As a thermodynamically stable solid, it maintains structural integrity under the demanding conditions required for industrial chemical processing.
Characterized as a wide-band-gap insulator, this compound is prized for its unique ability to dissolve alumina. Its role in lowering the melting point of electrolyte baths makes it an indispensable material in modern aluminum smelting operations.
Key Properties
Cross-validated computational properties for cryolite, 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 Na3AlF6. 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 Na3AlF6, 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. |
|---|---|---|---|---|---|
| — | — | 7.64 | 0.0000 | -3.396 | — |
| P21/c (No. 14) | monoclinic | 7.20 | 0.0000 | -3.331 | — |
| P21/c (No. 14) | monoclinic | 6.72 | 0.0000 | -5.313 | 3.06 |
| — | — | 7.70 | 0.0071 | -3.389 | — |
| R-3 (No. 148) | trigonal | 6.56 | 0.0120 | -5.301 | 2.99 |
| R-3 (No. 148) | trigonal | 7.06 | 0.0125 | -3.318 | — |
| Immm (No. 71) | orthorhombic | 5.89 | 0.0597 | -5.253 | 2.68 |
| Fm-3m (No. 225) | cubic | 5.89 | 0.0612 | -5.252 | 2.71 |
| — | — | 6.51 | 0.0647 | -3.331 | — |
| — | — | 6.55 | 0.0655 | -3.330 | — |
| Immm (No. 71) | orthorhombic | 6.26 | 0.0706 | -3.260 | — |
| P21/c (No. 14) | monoclinic | — | — | — | 2.99 |
Synthesis Routes
Literature-extracted synthesis procedures targeting Na3AlF6.
Applications
Where cryolite is used.
Frequently Asked Questions
Common questions about cryolite, answered from cross-validated data.
What is Na3AlF6?
Cryolite is a stable, insulating mineral compound primarily used as a flux to facilitate the electrolytic extraction of aluminum.
What is Na3AlF6 used for?
What is the band gap of Na3AlF6?
Is Na3AlF6 a metal, semiconductor, or insulator?
Is Na3AlF6 thermodynamically stable?
What is the crystal structure of Na3AlF6?
How many polymorphs of Na3AlF6 are known?
How is Na3AlF6 synthesized?
What elements does Na3AlF6 contain?
Where does the data for Na3AlF6 come from?
How It Compares
As a highly specialized fluoride compound, cryolite occupies a unique niche in materials science where it serves as the primary fluxing agent for industrial electrolysis, distinguishing itself through its exceptional chemical compatibility and stability in molten salt environments.
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)
- 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)
- 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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