电场作用下甲醇结构和扩散性质的分子动力学模拟

Molecular dynamics simulation of structural and dynamic properties of methanol under influence of external electric field

采用分子动力学模拟方法研究了外电场作用对甲醇的微观结构和动力学性质的影响. 模拟得到了外电场作用下甲醇分子微观构型的物理图像, 发现外电场的作用使甲醇分子的偶极向量沿电场作用方向有序排列. 随着电场强度的增加, 形成两氢键的甲醇分子的摩尔分数和氢键平均数目增加, O—H…O呈线形分布的概率增加,氢键的平均寿命延长, 外电场增强了甲醇分子间的氢键作用. 随着电场强度的增加, 分子的平动自扩散系数降低. 外电场作用的附加力阻碍了分子平动运动, 分子的平动运动表现为各向异性.

Molecular dynamics simulations of liquid methanol were performed at 298 K and density of 0.78 g&middotcm-3 under various applied external electric fields, ranging from 0 - 1010 V&middotm-10. Methanol was described by using the three-site OPLS potential model. The influence of the external field on structural and dynamic properties of methanol was investigated. An obvious structural change could be detected by the snapshots of methanol microscopic configuration without and with an electric field of 1.0 × 1010 V&middotm-1. Enhancement of the methanol hydrogen bond structure with increasing strength of the electric field was deduced from the radial distribution functions and the analysis of hydrogen bonds structure. The self-diffusion coefficient decreased with increasing strength of electric field, and the self-diffusion coefficient was anisotropic.