HPd
HPd is a thermodynamically stable metallic hydride formed from palladium and hydrogen.
About HPd
HPd is a metallic hydride compound that maintains thermodynamic stability as a phase on the convex hull. Its electronic character is defined by its metallic nature, lacking a band gap, which distinguishes it from insulating or semiconducting hydrides.
Due to its high structural diversity, this compound is a subject of significant interest in materials science. Researchers study its various configurations to understand the fundamental interactions between hydrogen and palladium atoms in solid-state systems.
Key Properties
Cross-validated computational properties for HPd, 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 HPd. 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 HPd, 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. |
|---|---|---|---|---|---|
| P63mc (No. 186) | hexagonal | 0.00 | 0.0000 | -13.297 | 9.53 |
| — | — | 0.00 | 0.0000 | -0.105 | — |
| — | — | 0.00 | 0.0168 | -0.089 | — |
| Fm-3m (No. 225) | cubic | 0.00 | 0.0178 | 0.002 | — |
| Fm-3m (No. 225) | cubic | 0.00 | 0.0331 | -13.264 | 10.29 |
| — | — | 0.00 | 0.0382 | -0.067 | — |
| — | — | 0.00 | 0.0390 | -0.066 | — |
| — | — | 0.00 | 0.2043 | 0.099 | — |
| — | — | 0.00 | 0.2051 | 0.100 | — |
| — | — | 0.00 | 0.5005 | 0.395 | — |
| — | — | 0.00 | 0.6274 | 0.522 | — |
| C2/m (No. 12) | monoclinic | — | — | — | 8.52 |
Applications
Where HPd is used.
Frequently Asked Questions
Common questions about HPd, answered from cross-validated data.
What is HPd?
HPd is a thermodynamically stable metallic hydride formed from palladium and hydrogen.
What is HPd used for?
What is the band gap of HPd?
Is HPd a metal, semiconductor, or insulator?
Is HPd thermodynamically stable?
What is the crystal structure of HPd?
How many polymorphs of HPd are known?
What elements does HPd contain?
Where does the data for HPd come from?
How It Compares
As a thermodynamically stable metallic hydride, HPd represents a fundamental building block in the study of palladium-hydrogen interactions. It serves as a primary reference point for understanding how hydrogen integrates into transition metal lattices without the presence of a band gap.
Data sources & attribution
- 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)
- jarvis — Data from JARVIS (jarvis.nist.gov), NIST. Cite: Choudhary et al., npj Comp. Mater. 6, 173 (2020). (LicenseRef-US-Gov-PD)
- 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)
- nomad — Data from NOMAD (nomad-lab.eu). Cite: Draxl & Scheffler, J. Phys. Mater. 2, 036001 (2019). (CC-BY-4.0)
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