水合锰(Ⅱ)结构的量子化学和ABEEM/MM研究
摘要
For the next-generation polarizable force field, atom-bond electronegativity equalization fluctuating charge force field (ABEEM/MM), and quantum chemistry method, an accurate Mn2+-H2O potential function was constructed, and its parameters were determined via fitting to quantum chemistry results. Then the potential function was employed to calculate the structure and binding energies of the hydrated manganous ionic clusters Mn2+(H2O) n ( n =1-12). The results were in good agreement with those from quantum chemistry. Furthermore, the structural properties of the Mn2+ aqueous solution were simulated using ABEEM/MM molecular dynamics. This includes the radial distribution function (RDF), angular distribution function (ADF), water structure, and charge distribution. The first and second peaks of Mn2+-O RDF are located at 0.218 nm and 0.435 nm. The coordination numbers for the first and second hydration shells, which were integrated from the RDF, are 7.03 and 17.74. The first and second peaks of the O-Mn2+-O ADF are located at 80° and 140°. These results are consistent with those from experimental measurements and other theoretical simulations. The water molecules in the first hydration shell were polarized by the Mn2+ ions, and their bond lengths were stretched, but their bond angles were reduced. Mn2+ does not measurably affect the structures of the water molecules outside the first hydration shell. Our analysis of the charge distributions showed that, compared with ABEEM-7P liquid water, the charges of the H atom and lone pairs vary more in the Mn2+ aqueous solution. Moreover, there was evident charge transfer between the Mn2+ ions and their adjacent water molecules.