Trihydrogen oxide is a predicted inorganic compound ofhydrogen andoxygen with the chemical formulaH3O.[2][3] This is still ahypothetical compound, one of the unstablehydrogen polyoxides. It is hypothesized that the compound could constitute a thin layer of metallic liquid around the cores ofUranus andNeptune, and that this could be the source of their magnetic fields.[4] Calculations indicate the stability ofH3O in solid, superionic, and fluid metallic states at the deep interior conditions of these planets.
Trihydrogen oxide has not been observed experimentally as of 2023, but its existence is predicted by calculation using the CALYPSO method.[5] The compound should be stable in the pressure range 450–600 GPa and could be produced by the reaction:
The compound is considered not a true moleculartrihydrogen oxide compound. Instead, each oxygen atom is linked by a strong (covalent) bond to only two hydrogen atoms, as awater molecule, and there are molecules ofdihydrogen inserted in the voids of the water molecules network.[6] Structurally, it is thus a2(H2O)·H2 stoichiometric combination.
At 600 GPa and 7000 K, the compound density is calculated to be 4.3 g/cm3. Molecular dynamics simulations were carried out at constant density for different temperatures:[6]
At 1000 K,H3O is anorthorhombic crystalline solid (space groupCmca).
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.
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 bydynamo 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.[7][8]
