用位-位记忆方程研究极性分子溶液的反常迁移率
Study of anomalous mobility of polar molecular solutions by means of the site-site memory equation formalism
摘要：
在这项工作中，记忆方程的方法被应用于理论研究的极性分子液体动力学的相互作用网站模型描述。该研究包括温度-密度（压力）的平移扩散系数D和取向弛豫时间t的无限稀释的乙腈和甲醇在水中的溶液，和甲醇在乙腈的依赖性。在温度和密度的范围内，采用SPC/E模型的水和乙腈和甲醇的优化站点站点电位进行计算。尽管使用的模型势和封闭关系的近似字符，该理论是能够定性地再现所有的主要特征的温度和密度依赖性的D和t在计算机和真实的实验中观察到的。特别地，对于甲醇在水中的D和t，获得了异常行为，即迁移率随密度（压力）的增加，而乙腈在水中或甲醇在乙腈中没有显示出与通常的偏差。根据Yamaguchi等人[J. Chem. Phys. 119（2003）1021]的概念解释了所观察到的分子迁移率的增强，即根据两种竞争的摩擦起源，其随着密度增加而相互作用：分别具有随着密度增加而增强和减弱的趋势的碰撞摩擦和介电摩擦。
英文摘要：
In this work, the memory equation approach is applied for theoretical study of dynamics of polar molecular liquids described by the interaction site model. The study includes the temperature-density(pressure) dependence of the translational diffusion coefficients D and orientational relaxation times t for infinitely dilute solutions of acetonitrile and methanol in water, and methanol in acetonitrile. Calculations are performed over the range of temperatures and densities employing the SPC/E model for water and optimized site-site potentials for acetonitrile and methanol. Despite an approximate character of the model potentials and closure relation used, the theory is able to reproduce qualitatively all main features of temperature and density dependences of D and t observed in computer and real experiments. In particular, anomalous behavior, i.e. the increase in mobility with density(pressure), is obtained for D and t of methanol in water, while acetonitrile in water or methanol in acetonitrile do not show deviations from the usual. The observed enhancement in the molecular mobility is interpreted in accordance with the concept by Yamaguchi et al. [J. Chem. Phys. 119 (2003) 1021], i.e. in terms of two competing origins of friction, which interplay with each other as density increases: the collisional and dielectric frictions that have tendency, respectively, to strengthen and weaken with increasing density.
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