HCl
Hydrochloric acid · Muriatic acid, Chlorohydric acid, Spirit of salt
Hydrochloric acid is a colorless, highly corrosive aqueous solution of hydrogen chloride gas. It is a fundamental industrial chemical widely utilized in chemical manufacturing, metal processing, and food production.
ClH
Overview
Key Properties
Cross-validated computational properties for Hydrochloric acid, 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.
2.58–5.82 eV
Range across DFT structures
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.
0.000 eV/atom
Best (lowest) across sources
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.
On hull (stable)
2 DFT sources
StructuresCount of reported calculated crystal structures for this formula, including alternate polymorphs, source databases, and observed space groups.
386
4 databases, 44 space groups
Crystallography
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 | 5.82 | 0.0000 | -3.436 | 1.51 |
| I4mm (No. 107) | tetragonal | 5.12 | 0.0273 | -5.308 | 1.48 |
| Imm2 (No. 44) | orthorhombic | 5.18 | 0.0536 | -3.383 | 1.14 |
| I4/mmm (No. 139) | tetragonal | 2.58 | 0.3282 | -3.108 | 1.29 |
| Fm-3m (No. 225) | cubic | 0.00 | 1.2793 | -2.157 | 2.60 |
| P21/c (No. 14) | Monoclinic | — | — | — | 2.37 |
| No. 0 | unknown | — | — | — | 0.37 |
| No. 0 | unknown | — | — | — | 0.38 |
| P1 (No. 1) | Triclinic | — | — | — | 3.64 |
| Cm (No. 8) | Monoclinic | — | — | — | 2.41 |
| Imm2 (No. 44) | Orthorhombic | — | — | — | 1.14 |
| R3m (No. 160) | Trigonal | — | — | — | 2.37 |
Uses
Applications
Where Hydrochloric acid is used.
Steel picklingProduction of organic compoundspH control and neutralizationRegeneration of ion exchange resinsFood processing
Reference
Frequently Asked Questions
Common questions about Hydrochloric acid, answered from cross-validated data.
What is HCl?
Hydrochloric acid is a colorless, highly corrosive aqueous solution of hydrogen chloride gas. It is a fundamental industrial chemical widely utilized in chemical manufacturing, metal processing, and food production.
More questions
What is HCl used for?
Hydrochloric acid (HCl) is used in steel pickling, production of organic compounds, pH control and neutralization, regeneration of ion exchange resins, and food processing.
What is the band gap of HCl?
Hydrochloric acid (HCl) has a DFT-computed band gap of 2.58–5.82 eV across 386 reported structures.
Is HCl a metal, semiconductor, or insulator?
With a wide band gap up to 5.82 eV it is an insulator / wide-band-gap material.
Is HCl thermodynamically stable?
Yes — Hydrochloric acid (HCl) sits on the convex hull (energy above hull 0 eV/atom), i.e. on hull (stable).
What is the crystal structure of HCl?
The lowest-energy reported polymorph of Hydrochloric acid (HCl) is orthorhombic symmetry, space group Cmc21 (No. 36).
What is the density of HCl?
The computed density of the ground-state structure of Hydrochloric acid (HCl) is 1.51 g/cm³.
How many polymorphs of HCl are known?
386 structures of HCl are reported across 4 databases, spanning 44 distinct space groups.
What elements does HCl contain?
Hydrochloric acid (HCl) contains Cl and H (2 elements).
Where does the data for HCl come from?
HCl data is cross-referenced from materials_project, mpaloe, cod.
Data sources & attribution
- materials_project — Data from the Materials Project. Cite: Jain et al., APL Materials 1, 011002 (2013).
- mpaloe — Data from mpaloe.
- cod — Data from the Crystallography Open Database. Cite: Grazulis et al., Nucleic Acids Res. 40, D420 (2012).
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