受限Lennard-Jones流体自扩散系数的分子动力学模拟

Molecular dynamics simulation of self-diffusion coefficient of confined Lennard-Jones fluid

基于平衡态分子动力学(EMD)方法,建立了受限空间中的Lennard-Jones(LJ)流体自扩散模型.采用径向分布函数对LJ流体微观结构进行了表征,模拟了LJ流体在纳米尺度受限空间中的自扩散系数,并将其与相应的自由空间内LJ流体自扩散系数进行了比较,同时从分子水平分析了温度、密度和受限尺度对自扩散系数的影响.研究结果表明:受限空间内LJ流体自扩散系数随受限尺度的增大而逐渐增大;与自由空间一样,受限LJ流体自扩散系数也随温度的升高而近似线性增加,随密度的增加而逐渐减小,但始终小于相同温度、密度条件下自由空间所对应值.并且根据文献中的实验数据验证了该模型的准确性.

A self-diffusion model of Lennard-Jones（LJ） fluid in confined space was developed by using equilibrium molecular dynamics（EMD） simulation method.The radial distribution function is utilized to analyze the LJ fluid microstructure.The self-diffusion coefficient of LJ fluid in the nanoscale confined space is calculated and compared with that in free space.The effects of temperature,density,and confined scale on the self-diffusion coefficient are all investigated and discussed at the molecular level.The results indicate that the LJ fluid self-diffusion coefficient in confined space increases with the increasing confined scale.Similar to that in free space,the LJ fluid self-diffusion coefficient in confined space also increases approximately in a linear fashion with temperature,while it decreases gradually with the increasing density.However,the LJ fluid self-diffusion coefficient in confined space is smaller than that in free space with the same temperature and density.In addition,the accuracy of the self-diffusion coefficient calculated by the present model is verified by the experimental data available in the literature.