RbCl溶液微观结构的分子动力学模拟

摘要

采用经典分子动力学、OPLS-AA全原子力场及TIP4P水模型,研究了300 K温度下无限稀释及1.0 mol/L的RbCl水溶液中Rb+与Cl-微观水合结构、水化及离子缔合特征.RbCl溶液中,水分子以氧原子去接近Rb+,而Cl-周围的水分子则以其中的一个氢原子去靠近.对模拟轨迹分析,获得了径向分布函数、配位数曲线、取向分布函数、水化因子等微观结构及水化信息.计算得到的Rb+和Cl-的第一水合层的水合距离及水合数分别为0.288、0.318 nm和7.30、7.17,对应的水化半径及水化数分别为0.270、0.290 nm和2.37、3.05.在1.0 mol/L的RbCl水溶液中,Rb+与Cl-之间存在直接接触和溶剂共享离子对,其Rb+与Cl-之间的特征距离分别为0.326和0.522 nm.采用Einstein法计算得到Rb+和Cl-的自扩散系数分别为(2.194±0.091 3)×10-5和(2.002±0.074 8)×10-5 cm2/s,计算得到的自扩散系数与实验值吻合很好.%Micro-hydrated structure of infinite diluted and 1.0 mol/L aqueous RbCl solution at 300 K were simulated with molecular dynamics simulations using OPLS-AA force field and TIP4P water model.The simulation time was up to 10 nanosecond and the simulation trajectories were analyzed in detail.Themicro-hydrated characteristcs were pictured by the RDF,coordination number function,orientation distribution functions,and hydration factors etc.The hydration distance and coordination numbers of Rb+ and Cl-are 0.288,0.318 nm and 7.295,7.169,respectively;their hydration numbers and hydration radii of Rb+ and Cl-are 2.37,3.05 and 0.270,0.290 nm.In aqueous RbCl solution of 1.0 moL/L,Contact Ion Pair (CIP) and Solvent Shared Ion Pairs (SIP)are found with characteristic vector distance between Rb+ and Cl-are 0.326 and 0.522 nm.The diffusion coefficients of Rb + and Cl-are 2.194 ± 0.091 3 × 10-5 and 2.002 ± 0.074 8 × 10-5 cm2/s,respectively,which are in good agreement with the experimental values.