ION-PAIR FORMATION IN WATER CLUSTERS - A THEORETICAL-STUDY

Two hydrated ion pairs of the formula (H3O+)(H2O)(3) (OH-) are studied using Hartree-Fock and MP2 wavefuctions with a 6-311 + + G* basis se t. Two neutral water pentamers are also studied for comparison. Thermo dynamics, IR spectra, dipole moments, rotational constants and spatial extent of the four clusters are examined in detail. Agreement of calc ulated thermodynamic quantities and TR spectra with experimental Value s is significant. The hydrated ion pairs are stablized more by electro n correlation than the neutral species. This can be partially explaine d in terms of the strained configuration of these hydrated ion pairs. The hydrated ion pairs also have a suprisingly small calculated dipole moment. (C) 1997 Elsevier Science B.V.