B5H9
Pentaborane · Pentaborane(9)
Pentaborane is a complex, insulating boron-hydrogen molecule that serves as a specialized hydride in chemical research.
About Pentaborane
Pentaborane is a volatile borane hydride characterized by its insulating electronic structure. As a member of the boron-hydrogen family, it represents a complex molecular hydride with significant interest in high-energy density applications and chemical synthesis.
Due to its near-hull thermodynamic stability, this compound is considered a viable target for synthesis and structural analysis. Its molecular architecture provides a distinct contrast to simpler binary hydrides, making it a subject of ongoing investigation within the broader field of hydrogen storage materials.
Key Properties
Cross-validated computational properties for Pentaborane, aggregated across 6 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 B5H9. 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 B5H9, 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. |
|---|---|---|---|---|---|
| I4mm (No. 107) | tetragonal | 5.50 | 0.0031 | -0.029 | — |
| P43 (No. 78) | tetragonal | 5.96 | 0.0192 | -4.907 | 0.73 |
| P41 (No. 76) | tetragonal | 5.96 | 0.0198 | -4.907 | 0.73 |
| I4mm (No. 107) | tetragonal | 5.71 | 0.0284 | -4.898 | 0.75 |
| — | — | 5.78 | 0.0351 | -0.037 | — |
| I4mm (No. 107) | tetragonal | 5.80 | — | -4.622 | 0.71 |
| P41 (No. 76) | tetragonal | — | — | — | 0.81 |
| I4mm (No. 107) | tetragonal | — | — | — | 0.74 |
| I4mm (No. 107) | tetragonal | — | — | — | 0.74 |
| I4mm (No. 107) | tetragonal | — | — | — | 0.74 |
| I4mm (No. 107) | tetragonal | — | — | — | 0.76 |
Applications
Where Pentaborane is used.
Frequently Asked Questions
Common questions about Pentaborane, answered from cross-validated data.
What is B5H9?
Pentaborane is a complex, insulating boron-hydrogen molecule that serves as a specialized hydride in chemical research.
What is B5H9 used for?
What is the band gap of B5H9?
Is B5H9 a metal, semiconductor, or insulator?
Is B5H9 thermodynamically stable?
What is the crystal structure of B5H9?
What is the density of B5H9?
How many polymorphs of B5H9 are known?
What elements does B5H9 contain?
Where does the data for B5H9 come from?
How It Compares
Within the hydrogen storage hydrides class.
Unlike the simple ionic or metallic hydrides such as LiH or CaH2, which typically feature high lattice stability, B5H9 exists as a complex molecular species. It shares more structural commonality with BH3 than with the solid-state saline hydrides like MgH2 or AlH3, reflecting the unique covalent bonding nature inherent to boron-rich hydrides.
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)
- materials_project — Data from the Materials Project (materialsproject.org). Cite: Jain et al., APL Materials 1, 011002 (2013). (CC-BY-4.0)
- 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)
- aflow — Data from AFLOW (aflow.org). Cite: Curtarolo et al., Comp. Mater. Sci. 58, 218 (2012). (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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