The onset of dissociation in the aqueous LiOH clusters: a solvation study with the effective fragment potential model and quantum mechanics methods

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• 作者：Yoshikawa ; Akihiko ; Morales ; Jorge A.
• 关键词：Effective fragment potential model ; Solvation effects ; Spontaneous dissociation of ionic compounds in aqueous clusters ; Charge transfer
• 刊名：Journal of Molecular Structure: THEOCHEM
• 出版年：2004
• 出版时间：July 26, 2004
• 年：2004
• 卷：681
• 期：1-3
• 页码：27-40
• 全文大小：543 K

文摘

The first systematic study on the solvation of the LiOH(H₂O)_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 H₂O 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.