Yan Liuming, Shao Changle, Ji Xiaobo
Department of Chemistry, College of Sciences, Shanghai University, 99 Shangda Road, Shanghai 200444, China.
J Comput Chem. 2009 Jul 15;30(9):1361-70. doi: 10.1002/jcc.21157.
The electroosmotic drag coefficient of water molecules in hydrated sodium perfluorosulfonate electrolyte polymer is evaluated on the basis of the velocity distribution functions of the sodium cations and water molecules with an electric field applied using molecular dynamics simulations. The simulation results indicate that both velocity distribution functions of water molecules and of sodium cations agree well with the classic Maxwellian velocity distribution functions when there is no electric field applied. If an electric field is applied, the distribution functions of velocity component in directions perpendicular to the applied electric field still agree with the Maxwellian velocity distribution functions but with different temperature parameters. In the direction of the applied electric field, the electric drag causes the velocity distribution function to deviate from the Maxwellian velocity distribution function; however, to obey the peak shifted Maxwellian distribution function. The peak shifting velocities coincide with the average transport velocities induced by the electric field, and could be applied to the evaluation of the electroosmotic drag coefficient of water. By evaluation of the transport velocities of water molecules in the first coordination shells of sodium cations, sulfonate anion groups, and in the bulk, it is clearly shown that the water molecules in the first coordination shell of sodium cations are the major contribution to the electroosmotic drag and momentum transfer from water molecules within the first coordination shell to the other water molecules also contributes to the electroosmotic drag.
基于使用分子动力学模拟施加电场时钠离子和水分子的速度分布函数，对水合全氟磺酸锂电解质聚合物中水分子的电渗拖曳系数进行了评估。模拟结果表明，当不施加电场时，水分子和钠离子的速度分布函数均与经典的麦克斯韦速度分布函数吻合良好。如果施加电场，垂直于施加电场方向的速度分量分布函数仍与麦克斯韦速度分布函数吻合，但温度参数不同。在施加电场的方向上，电拖曳使速度分布函数偏离麦克斯韦速度分布函数；然而，服从峰值移动的麦克斯韦分布函数。峰值移动速度与电场诱导的平均传输速度一致，可用于评估水的电渗拖曳系数。通过评估钠离子、磺酸根阴离子基团第一配位层以及本体中水分子的传输速度，清楚地表明钠离子第一配位层中的水分子对电渗拖曳起主要作用，并且从第一配位层中的水分子到其他水分子的动量传递也对电渗拖曳有贡献。
