受限空间分子自扩散性质的耗散粒子动力学模拟

Dissipative particle dynamics simulation of molecule self-diffusion under cylindrical confinement

基于耗散粒子动力学模拟研究了强排斥壁面作用下圆管状受限空间内单粒子及柔性链分子自扩散系数的变化规律,并对空间受限作用下分子扩散性质的各向异性进行了深入分析.结果表明,随着圆管管径的增大,单粒子及柔性链分子的自扩散系数均呈现先减小后增大的变化规律,且出现自扩散系数最小值对应的管径随链长的增加逐渐减小;柔性链分子因其在圆管中异于体相的伸展状况,自扩散系数的变化幅度随链长的增加而变大;圆管中分子径向自扩散系数随管径的增大逐渐增大,并与管径近似为指数关系,分子轴向自扩散系数则随管径的增大先减小后逐渐收敛于体相自扩散系数.

The self-diffusion coefficient of molecules of one bead or flexible chain type under cylindrical confinement with strong exclusion interface was simulated by dissipative particle dynamics, and the anisotropy of molecular self-diffusion was analyzed in detail. The simulation results show that the self-diffusion coefficients of molecules of one bead or flexible chain type first decreased and then increased with the increase of the cylinder radius, and the cylinder radius corresponding to the minimum self-diffusion coefficient decreased with the increase of molecule length. The variation range of the self-diffusion coefficient of flexible chain molecules was amplified with the increase of the molecule length, due to the difference of their extension between the confinement and the bulk state. With the increase of the cylinder radius, the radial self-diffusion coefficient increased and approximately has an exponential relationship with the cylinder radius; the axial self-diffusion coefficient first decreased and then gradually converged to the bulk self-diffusion coefficient.