HC2
HC2 is a semiconducting carbon-hydrogen compound that exhibits high structural diversity despite being thermodynamically unstable.
About HC2
HC2 is a carbon-hydrogen compound characterized by its semiconducting electronic nature. Despite its relatively simple elemental composition, it exhibits significant structural complexity as evidenced by the hundreds of reported configurations across various databases.
Due to its position relative to the thermodynamic hull, this material is considered metastable or unstable under standard conditions. Its study remains a point of interest for researchers investigating the diverse bonding possibilities within carbon-based systems.
Key Properties
Cross-validated computational properties for HC2, 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 HC2. 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 HC2, 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. |
|---|---|---|---|---|---|
| — | — | 2.54 | 0.1000 | -0.006 | — |
| P21/c (No. 14) | monoclinic | 2.46 | 0.1074 | -7.782 | 1.34 |
| C2/m (No. 12) | monoclinic | 0.00 | 0.1492 | -7.740 | 1.43 |
| C2/m (No. 12) | monoclinic | 0.00 | 0.1496 | 0.060 | — |
| R-3m (No. 166) | trigonal | 0.00 | 0.4671 | 0.377 | — |
| Pm (No. 6) | monoclinic | 0.00 | 1.7420 | 1.652 | — |
| — | — | 0.00 | 3.0973 | 2.991 | — |
| — | — | 0.00 | 3.5607 | 3.455 | — |
| P1 (No. 1) | triclinic | — | — | — | 2.27 |
| Cm (No. 8) | monoclinic | — | — | — | 2.45 |
| Cm (No. 8) | monoclinic | — | — | — | 2.61 |
| Pm (No. 6) | monoclinic | — | — | — | 2.05 |
Applications
Where HC2 is used.
Frequently Asked Questions
Common questions about HC2, answered from cross-validated data.
What is HC2?
HC2 is a semiconducting carbon-hydrogen compound that exhibits high structural diversity despite being thermodynamically unstable.
What is HC2 used for?
What is the band gap of HC2?
Is HC2 a metal, semiconductor, or insulator?
Is HC2 thermodynamically stable?
What is the crystal structure of HC2?
What is the density of HC2?
How many polymorphs of HC2 are known?
What elements does HC2 contain?
Where does the data for HC2 come from?
How It Compares
As an unclassified material, HC2 represents a unique case study in carbon-hydrogen chemistry. Unlike more stable, well-defined hydrocarbons, its structural diversity suggests a complex energy landscape that distinguishes it from more conventional, thermodynamically favored phases.
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)
- materials_project — Data from the Materials Project (materialsproject.org). Cite: Jain et al., APL Materials 1, 011002 (2013). (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.
Analyze HC2 in the Lattice Graph platform
Polymorph comparison, confidence scoring, supply-chain risk, and patent monitoring — across 85 source databases.
Explore the Platform →