Structure reorganization dynamics of water clusters upon vertical ionization: Quantum chemical investigation

Quantum dynamics simulations of (H₂O) _n ⁺ water cluster cations comprising up to six molecules with the initial configurations of stable neutral isomers are combined with stationary calculations of the same cations in order to get nonempirical information about water cluster relaxation after the absorption of energy in a range of from 11.0 to 12.0 eV. The electronic problem was solved and the potential energy of the system was estimated in terms of the restricted or unrestricted Hartree-Fock approximation with the 6–31++G** atomic basis set taking into account second-order Möller-Plesset perturbation theory corrections. Calculations of dynamic trajectories were based on the Born-Oppenheimer approximation. The formation of stable water cluster cations is shown to be a multistage process, the principal stages of which are qualitatively correctly reflected by the sequence of steps in cation geometry optimization runs.