Abstract :
An accurate diatomics-in-molecules (DIM) representation of the first five potential energy surfaces of H2O in the singlet state is embedded in a DIM model (with induction interactions) for O (1Dg) in a solid hydrogen environment. We suggest that the absence of a barrier to formation of H2O from O (1Dg) + H2 in the isolated triatomic system is fully compatible with the existence of a stable O (1Dg) atom at a substitution site in the solid hydrogen crystal. This results from the requirement that, along the path to formation of H2O, the wave function must acquire ionic character, since H2O is a very polar molecule, but these ionic structures are penalised energetically in the many-body environment because of 3-body electrostatic interactions, effectively blocking the reaction path and conferring stability upon the O (1Dg) atom.
