应用从头算方法和ABEEM/MM浮动电荷分子力场,研究了水合碱上离子团簇Sr2+/Ba2+(H2O)n(n=1-6),构建了离子-水相互作用的ABEEM/MM势能函数,获得了水合离子团簇的稳定结构,计算了结能.计算结果表明,ABEEM/MM方法的结果和从头算方法的结果有很好的一致性.进一步应用ABEEM/MM对Sr2+和Ba2+水溶液进行了分子动力学模拟.对Sr2+水溶液,得到的Sr2+-水中氧原子的径向分布函数的第一和第二最高峰分别位于0.257和0.464 nm处,第一和第二水合层的配位水分子数分别为9.2和11.4;对Ba2+水溶液,得到的Ba2+与水中氧原子的径向分布函数的第一和第二最高峰分别位于0.269和0.467 nm处,第一和第二水合层的配位水分子数分别为9.9和12.4.这与实验值或其它理论模拟结果有较好的一致性.对比外层的水分子,金属离子的极化作用使得溶液中第一水合层中水分子的O-H键长增长,HOH键角减小.%Hydrated clusters of Sr2+/Ba2+(H2O)n (n=1-6) were investigated by the ab initio method and the ABEEM/MM fluctuating charge molecular force field.ABEEM/MM potential functions of cation-water interactions were constructed based on the stable structures and binding energies of the hydrated clusters were obtained.The results from ABEEM/MM are consistent with those from the ab initio method.Furthermore, Sr2+ and Ba2+ aqueous solutions were studied by ABEEM/MM molecular dynamic simulations.Results show that for the Sr2+ aqueous solution the first and second peaks of the SrO radial distribution function (RDF) are located at 0.257 and 0.464 nm, respectively.The coordination numbers of the water molecules for the first and second hydration shells are 9.2 and 11.4, respectively.For the Ba2+ aqueous solution, the first and second peaks of the BaO RDF are located at 0.269 and 0.467 nm, respectively.The coordination numbers of water molecules for the first and second hydration shells are 9.9 and 12.4,respectively.These results also show good consistency with experimental observations and other theoretical simulations.Compared with the external water molecules, the water molecules in the first hydration shell are evidently polarized by the cation and their O-H bond lengths are stretched while the HOH bond angles are found to be reduced.
展开▼
