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Trihydrogen oxide is a predicted inorganic compound of hydrogen and oxygen with the chemical formula H₃O. This is still a hypothetical compound, one of the unstable hydrogen polyoxides. It is hypothesized that the compound could constitute a thin layer of metallic liquid around the cores of Uranus and Neptune, and that this could be the source of their magnetic fields. Calculations indicate the stability of H₃O in solid, superionic, and fluid metallic states at the deep interior conditions of these planets.

Synthesis

Trihydrogen oxide has not been observed experimentally as of 2023, but its existence is predicted by calculation using the CALYPSO method. The compound should be stable in the pressure range 450–600 GPa and could be produced by the reaction:

2H₂O + H₂ → 2H₃O

Physical properties

The compound is considered not a true molecular trihydrogen oxide compound. Instead, each oxygen atom is linked by a strong (covalent) bond to only two hydrogen atoms, as a water molecule, and there are molecules of dihydrogen inserted in the voids of the water molecules network. Structurally, it is thus a 2(H₂O)·H₂ stoichiometric combination.

At 600 GPa and 7000 K, the compound density is calculated to be 4.3 g/cm. Molecular dynamics simulations were carried out at constant density for different temperatures:

• At 1000 K, H₃O is an orthorhombic crystalline solid (space group Cmca).
• At 1250 K, this solid passes into a superionic state.
• The compound liquefies at 5250 K, and the liquid should have metallic-like electrical conductivity.

In the Solar system

The magnetic fields of both Uranus and Neptune are special—non-dipolar and non-axisymmetric. This fact can be explained if the magnetic fields are produced by dynamo effect within a sufficiently thin conductive layer. However, the origin of the fields is still problematic because the cores of these planets are probably solid (thus too rigid), and the thick mantles of ice are too poorly conductive to create the effect.

References

1. "Hydronium radical".
2. Stuart, Sam (11 September 2013). Nomenclature of Inorganic Chemistry: Inorganic Chemistry Division Commission on Nomenclature of Inorganic Chemistry. Elsevier. ISBN 978-1-4832-8447-7. Retrieved 17 May 2023.
3. Steinberg, Paul (21 April 2015). A Salamander's Tale: My Story of Regeneration?Surviving 30 Years with Prostate Cancer. Simon & Schuster. ISBN 978-1-63220-953-5. Retrieved 17 May 2023.
4. Krämer, Katrina (9 March 2020). "Metallic trihydrogen oxide could explain ice giants' strange magnetic fields". Chemistry World. Retrieved 17 May 2023.
5. Wang, Yanchao; Lv, Jian; Zhu, Li; Ma, Yanming (1 October 2012). "CALYPSO: A method for crystal structure prediction". Computer Physics Communications. 183 (10): 2063–2070. arXiv:1205.2264. Bibcode:2012CoPhC.183.2063W. doi:10.1016/j.cpc.2012.05.008. ISSN 0010-4655. S2CID 44427602. Retrieved 17 May 2023.
6. ^ Huang, Peihao; Liu, Hanyu; Lv, Jian; Li, Quan; Long, Chunhong; Wang, Yanchao; Chen, Changfeng; Ma, Yanming (16 August 2019). "Metallic liquid H₃O in a thin-shell zone inside Uranus and Neptune". arXiv:1908.05821 .
7. Stanley, Sabine; Bloxham, Jeremy (March 2004). "Convective-region geometry as the cause of Uranus' and Neptune's unusual magnetic fields". Nature. 428 (6979): 151–153. Bibcode:2004Natur.428..151S. doi:10.1038/nature02376. ISSN 1476-4687. PMID 15014493. S2CID 33352017. Retrieved 17 May 2023.
8. Stanley, Sabine; Bloxham, Jeremy (1 October 2006). "Numerical dynamo models of Uranus' and Neptune's magnetic fields". Icarus. 184 (2): 556–572. Bibcode:2006Icar..184..556S. doi:10.1016/j.icarus.2006.05.005. ISSN 0019-1035. Retrieved 17 May 2023.

• Inorganic compounds
• Oxides
• Polyoxides
• Oxoacids
• Hypothetical chemical compounds
• Theoretical chemistry