模拟扩散系数的分子动力学方法

Molecular Dynamics Method for Simulating Diffusivities

在分析当前应用的各类分子动力学方法的基础上提出一个2参数(即温度松弛时间和压力松弛时间)模型,采用正交实验确定了最优的模型参数,压力与温度松弛时间的最优值均为2fs.在最优条件下跟踪系统的体积变化,最大波动在10%之内.将该模型应用于不同温度下氩及超临界二氧化碳自扩散系数模拟,并用动力学理论对自扩散系数与温度、压力的关系进行了定性分析,结果与实验值吻合.说明新模型具有稳定而准确的特点.

A new two-parameters, namely temperature and pressure relaxation times, model was proposed based on the basis of the isothermal-isobaric MD methods and both the parameters optimized by using the orthogonal test are 2 fs. The maximal deviation of system volume simulated under the optimal conditions was within the limit of 10%. ]＇he new model was used to simulate the selfdiffusion coefficients of argon and supercritical carbon dioxide at different temperatures, and the influence of temperature and pressure on selfdiffusion coefficients was analyzed qualitatively by the use of the kinetics theory. Good agreement is obtained between the simulated results and the experimentally measured data.