KAlH4
Potassium alanate · Potassium aluminum hydride
KAlH4 is a stable complex metal hydride used primarily as a solid-state material for hydrogen storage.
About Potassium alanate
Potassium alanate is a crystalline complex hydride that serves as a significant candidate for solid-state hydrogen storage. As an insulating material with a wide electronic band gap, it provides a stable framework for the reversible uptake and release of hydrogen gas, which is essential for developing efficient energy carriers.
Its thermodynamic stability on the convex hull distinguishes it as a robust compound within the alanate family. This stability makes it a subject of extensive structural research, with multiple confirmed arrangements reported across various databases, highlighting its importance in materials science for hydrogen economy applications.
Key Properties
Cross-validated computational properties for Potassium alanate, 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 KAlH4. 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 KAlH4, 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. |
|---|---|---|---|---|---|
| — | — | 5.06 | 0.0000 | -0.196 | — |
| Pnma (No. 62) | orthorhombic | 5.06 | 0.0000 | -0.310 | — |
| Pnma (No. 62) | orthorhombic | 5.05 | 0.0000 | -4.704 | 1.28 |
| I41/a (No. 88) | tetragonal | 4.78 | 0.0014 | -0.308 | — |
| — | — | 4.72 | 0.0037 | -0.192 | — |
| I41/a (No. 88) | tetragonal | 4.80 | 0.0048 | -4.700 | 1.31 |
| — | — | 4.35 | 0.0233 | -0.173 | — |
| Pnma (No. 62) | orthorhombic | — | — | — | 1.22 |
| I41/a (No. 88) | tetragonal | — | — | — | 1.24 |
| Pnma (No. 62) | orthorhombic | — | — | — | 1.22 |
| I41/a (No. 88) | tetragonal | — | — | — | 1.28 |
| Pnma (No. 62) | orthorhombic | — | — | — | 1.21 |
Applications
Where Potassium alanate is used.
Frequently Asked Questions
Common questions about Potassium alanate, answered from cross-validated data.
What is KAlH4?
KAlH4 is a stable complex metal hydride used primarily as a solid-state material for hydrogen storage.
What is KAlH4 used for?
What is the band gap of KAlH4?
Is KAlH4 a metal, semiconductor, or insulator?
Is KAlH4 thermodynamically stable?
What is the crystal structure of KAlH4?
How many polymorphs of KAlH4 are known?
What elements does KAlH4 contain?
Where does the data for KAlH4 come from?
How It Compares
Within the hydrogen storage hydrides class.
Within the class of hydrogen storage hydrides, KAlH4 occupies a distinct position compared to simpler binary hydrides like LiH or MgH2. While binary hydrides often require extreme conditions for hydrogen cycling, the complex structure of KAlH4 allows for more nuanced kinetic and thermodynamic tuning, positioning it as a more versatile alternative to simpler metal hydrides in high-density storage research.
Related Compounds
Other Hydrogen Storage Hydrides in the database.
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)
- cod — Data from the Crystallography Open Database (crystallography.net/cod/). Cite: Grazulis et al., J. Appl. Cryst. 42, 726 (2009). (CC0-1.0)
- mpaloe — Data from MP-ALOE. Cite: Kuner et al., npj Comput. Mater. (2025), doi:10.1038/s41524-025-01834-9.
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