H2CO3
carbonic acid · dihydrogen carbonate
Carbonic acid is a transient, insulating chemical compound that serves as a crucial intermediate in the conversion of carbon dioxide into aqueous carbonate species.
About carbonic acid
Carbonic acid is a fundamental chemical species formed through the hydration of carbon dioxide. As a wide-gap insulating material, it plays a critical role in maintaining the pH balance of natural waters and biological fluids through its reversible dissociation behavior.
Despite its transient nature in standard environments, the compound is considered thermodynamically near-hull, suggesting it is a viable target for synthesis under specific conditions. Its existence across multiple reported structural configurations highlights its importance in high-pressure research and fundamental molecular chemistry.
Key Properties
Cross-validated computational properties for carbonic acid, 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.
Reported Structures
Lowest-energy structures reported for H2CO3, 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. |
|---|---|---|---|---|---|
| Cmcm (No. 63) | orthorhombic | 5.90 | 0.0047 | -6.664 | 1.71 |
| Cmcm (No. 63) | — | — | — | — | — |
| Cmcm (No. 63) | Orthorhombic | — | — | — | 1.40 |
| Cmcm (No. 63) | Orthorhombic | — | — | — | 1.39 |
| Cmcm (No. 63) | Orthorhombic | — | — | — | 1.44 |
Applications
Where carbonic acid is used.
Frequently Asked Questions
Common questions about carbonic acid, answered from cross-validated data.
What is H2CO3?
Carbonic acid is a transient, insulating chemical compound that serves as a crucial intermediate in the conversion of carbon dioxide into aqueous carbonate species.
What is H2CO3 used for?
What is the band gap of H2CO3?
Is H2CO3 a metal, semiconductor, or insulator?
Is H2CO3 thermodynamically stable?
What is the crystal structure of H2CO3?
What is the density of H2CO3?
How many polymorphs of H2CO3 are known?
What elements does H2CO3 contain?
Where does the data for H2CO3 come from?
How It Compares
As a unique chemical entity, carbonic acid serves as the primary bridge between inorganic carbon dioxide and organic carbonates, functioning as a central component in the global carbon cycle without direct structural analogs in this specific class.
Data sources & attribution
- materials_project — Data from the Materials Project. Cite: Jain et al., APL Materials 1, 011002 (2013).
- jarvis — Data from JARVIS (NIST). Cite: Choudhary et al., npj Comp. Mater. 6, 173 (2020).
- mpaloe — Data from mpaloe.
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