Theoretical Studies On The Hydrations Of Iodide And Alklaine Metal Ions

Ionic solvation in aqueous solution plays important roles in a wide range of chemical and biological processes. In this dissertation, the hydrated iodide and alkaline metal ions systems were studied by quantum chemistry and molecular mechanics.The properties of hydrated clusters of iodide, I^-(H₂O)_n (n=1⁶), in gas phase were investigated by MP2 and B3LYP methods with 6-311++G(d, p) basis set(the pseudo potential basis set LANL2DZ was employed for I^-), including the structures and vibrational frequencies. The energies of the most stable structures were calculated at MP2/6-311++G(2d, 2p) level. The I^--H₂O interaction potential was constructed in terms of atom-bond electronegatibity equalization fluctuating charge molecular force field(ABEEM/MM). Then, the ABEEM/MM potential function was applied to calculate the binding energies of the hydrated iodide chusters, and the results show that the structures and binding energies from ABEEM/MM are consistent with those of quantum chemistry. Furthermore, the constructed I^--H₂O potential was used into the dynamics simulations of the iodide aqueous solution. The results show that the first and second peaks of the radial distribution function (RDF)of I^--H are located at 0.29 and 0.41 nm, respectively; the first and second peaks of I^--O RDF are located at 0.39 and 0.45 nm, respectively; the coordination number of water molecules for the first and second hydration shell is 8.45 and 9.4, respectively, which show good consistency with those of the experiment and other simulations.The gas-phase hydrated alkaline metal cation clusters, M+(H₂O)_n(M= Li,Na,K,Rb,Cs;n=1⁶) were investigated by MP2/aug-cc-pVDZ(the pseudo potential basis set LANL2DZ was employed for M⁺, excepted for Na⁺), and the geometries were optimized. The vibrational frequencies and the binding energies were calculated for the lowest-energy structures of the hydrated clusters. The results show that as the hydration number increases, the average distance of M⁺-O gradually increases, while the total binding energy gradually decreases.