THEORETICAL-STUDY OF DIRECT AND WATER-ASSISTED ISOMERIZATION OF FORMALDEHYDE RADICAL-CATION - A COMPARISON BETWEEN DENSITY-FUNCTIONAL AND POST-HARTREE-FOCK APPROACHES

A recently introduced density functional incorporating gradient corrections and some Hartree-Fock exchange has been used to study the isomerization of formaldehyde radical cation to its distonic form. Both direct and water-assisted mechanisms have been considered. Structural and energetic quantities computed by the new functional approach those provided by the much more expensive coupled cluster method and represent a significant improvement over the results obtained by standard density functionals and perturbative post-Hartree-Fock methods. Non-potential energy effects have also been considered, but their role is marginal.