RbCl溶液微观结构的分子动力学模拟

Molecular Dynamics Study on RbCl Micro-hydrated Structure

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)×10-5cm^2/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 characteristics 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 ra- dii of Rb ＋ and Cl- are 2.37,3.05 and 0. 270,0. 290 nm. In aqueous RbCl solution of 1.0 mol/L, Con- tact Ion Pair （CIP） and Solvent Shared Ion Pairs（SIP） are found with characteristic vector distance be- tween 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.