The first systematic study on the solvation of the LiOH(H 2O)n (n=1-6,8) clusters is herein presented by using both the molecular-mechanics effective fragment potential (EFP) model and full quantum mechanics methods. Aqueous clusters are sequentially calculated first with the LiOH solute molecule described by a restricted Hartree-Fock (RHF) wavefunction and the H2O solvent molecules by the EFP model (EFP/RHF), and then with the full quantum mechanics RHF and Møller-Pleset second-order perturbation (MP2) theories. Calculated properties include equilibrium geometries, Mulliken charges, bond lengths and orders, and relative energies inter alia. Present results indicate that at the least six H 2O molecules are necessary to be added to one LiOH molecule to cause its spontaneous dissociation into a Li+/OH- separated ion pair. Another instance of dissociation is also observed in one of the LiOH(H2O)8 isomers. EFP/RHF reasonably reproduces RHF structural properties and dissociation patterns but discrepancies arise in the solute charge description. Comparisons of the present theoretical results with previous EFP studies and with a few experimental data are also discussed.
- Charge transfer
- Effective fragment potential model
- Solvation effects
- Spontaneous dissociation of ionic compounds in aqueous clusters