CaHI
CaHI is a thermodynamically stable, insulating ternary hydride used in research for advanced solid-state hydrogen storage applications.
About CaHI
CaHI is a distinct inorganic compound classified within the hydrogen storage hydrides family. As a thermodynamically stable phase residing on the convex hull, it represents a robust structural arrangement that is of significant interest for materials scientists investigating solid-state hydrogen containment. Its electronic character is defined as a wide-band-gap insulator, which influences its chemical reactivity and potential for integration into specialized storage systems.
This material serves as a critical subject for understanding the complex interactions between calcium, hydrogen, and iodine within a crystalline lattice. Its stability profile makes it a compelling candidate for fundamental research into how halide incorporation modifies the properties of traditional metal hydrides, potentially offering pathways to tune hydrogen release and uptake kinetics for future energy storage technologies.
Key Properties
Cross-validated computational properties for CaHI, aggregated across 4 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 CaHI. 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 CaHI, 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. |
|---|---|---|---|---|---|
| P4/nmm (No. 129) | tetragonal | 3.62 | 0.0000 | -1.230 | — |
| — | — | 3.32 | 0.0000 | -1.181 | — |
| P4/nmm (No. 129) | tetragonal | 3.53 | 0.0431 | -3.549 | 3.69 |
| — | — | 3.45 | 0.0648 | -1.116 | — |
| — | — | 3.46 | 0.0771 | -1.104 | — |
| P4/nmm (No. 129) | tetragonal | — | — | — | 3.76 |
Applications
Where CaHI is used.
Frequently Asked Questions
Common questions about CaHI, answered from cross-validated data.
What is CaHI?
CaHI is a thermodynamically stable, insulating ternary hydride used in research for advanced solid-state hydrogen storage applications.
What is CaHI used for?
What is the band gap of CaHI?
Is CaHI a metal, semiconductor, or insulator?
Is CaHI thermodynamically stable?
What is the crystal structure of CaHI?
How many polymorphs of CaHI are known?
What elements does CaHI contain?
Where does the data for CaHI come from?
How It Compares
Within the hydrogen storage hydrides class.
Within the diverse class of hydrogen storage hydrides, CaHI occupies a unique niche compared to more conventional binary systems like CaH2 or LiH. While simple hydrides such as MgH2 and AlH3 are widely recognized for their high hydrogen density, the inclusion of iodine in the CaHI framework alters the structural and electronic landscape, setting it apart from simpler compounds like BH3 or H3N. It represents a more complex ternary approach to hydride chemistry, contrasting with the binary nature of CaClH by balancing halide-induced stability with the requirements for effective hydrogen storage.
Related Compounds
Other Hydrogen Storage Hydrides in the database.
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)
- 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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