HCl
Hydrogen chloride · Chlorane, Hydrochloric acid
Hydrogen chloride is a stable, insulating diatomic compound that serves as a vital precursor in the production of numerous industrial chemicals.
About Hydrogen chloride
Hydrogen chloride is a fundamental inorganic compound that exists as a thermodynamically stable species. Its electronic character defines it as a wide-gap insulator, reflecting its strong covalent bonding and distinct chemical reactivity in various states of matter.
This compound is widely utilized across chemical manufacturing and industrial synthesis. Due to its high stability and well-documented structural behavior, it serves as a critical building block for producing a vast array of chlorine-based chemical products and reagents.
Key Properties
Cross-validated computational properties for Hydrogen chloride, 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 HCl. 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 HCl, 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. |
|---|---|---|---|---|---|
| Cmc21 (No. 36) | orthorhombic | 5.97 | 0.0000 | -3.436 | 1.51 |
| — | — | 5.87 | 0.0000 | -0.673 | — |
| Cmc21 (No. 36) | orthorhombic | 5.82 | 0.0000 | -0.454 | — |
| — | — | 5.97 | 0.0005 | -0.672 | — |
| Pc (No. 7) | monoclinic | 5.68 | 0.0164 | -0.438 | — |
| I4mm (No. 107) | tetragonal | 5.95 | 0.0273 | -5.308 | 1.48 |
| I4mm (No. 107) | tetragonal | 5.29 | 0.0314 | -0.423 | — |
| — | — | 5.33 | 0.0472 | -0.626 | — |
| Imm2 (No. 44) | orthorhombic | 5.18 | 0.0536 | -3.383 | 1.14 |
| — | — | 4.01 | 0.0964 | -0.576 | — |
| P4mm (No. 99) | tetragonal | 6.53 | 0.1696 | -0.284 | — |
| I4/mmm (No. 139) | tetragonal | 2.94 | 0.3282 | -3.108 | 1.29 |
Applications
Where Hydrogen chloride is used.
Patent Landscape
24 patents reference HCl or close compositional variants.
| Patent | Title | Assignee | Granted |
|---|---|---|---|
| 4241031 | Dissolution of nickeliferous sulfide material in HCl | — | — |
| 5421964 | Process for separating HCl and halocarbons | — | — |
| 4113588 | Process for recovery of waste H.sub.2 SO.sub.4 and HCl | — | — |
| 5316998 | HCl adsorbent and method for making and using same | — | — |
| 4839153 | Process for purification of HCl from pyrolysis of EDC | — | — |
| 9353425 | Processes for preparing alumina and magnesium chloride by HCl leaching of various materials | — | — |
| 10112842 | Process to produce magnesium compounds, and various by-products using sulfuric acid in a HCl recovery loop | — | — |
| 4714604 | Method of separating HF and SiF.sub.4 from HCl | — | — |
| 4177119 | Process for recovery of waste H.sub.2 SO.sub.4 and HCl | — | — |
| 5391363 | Continuous purification of an off-gas composed of CO.sub.2 +HCl+COCl.sub.2 | — | — |
Frequently Asked Questions
Common questions about Hydrogen chloride, answered from cross-validated data.
What is HCl?
Hydrogen chloride is a stable, insulating diatomic compound that serves as a vital precursor in the production of numerous industrial chemicals.
What is HCl used for?
What is the band gap of HCl?
Is HCl a metal, semiconductor, or insulator?
Is HCl thermodynamically stable?
What is the crystal structure of HCl?
How many polymorphs of HCl are known?
What elements does HCl contain?
Where does the data for HCl come from?
How It Compares
As a primary inorganic molecule, hydrogen chloride occupies a central role in chemical science. It is a highly characterized substance that serves as a benchmark for understanding simple diatomic bonding and reactivity patterns within the broader landscape of inorganic chemistry.
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)
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