L-J流体自扩散系数及其与温度关系的分子动力学模拟

扩散系数在化工设计和研究中是不可缺少的传递特性。但其数据却相对缺乏,因此需要寻找一种方法来预测这个特性就显得十分重要。利用分子动力学方法模拟了简单流体的自扩散系数。模拟分别采用Green-Kubo法(VACF:velocity autocorrelation function)和Einstein法(MSD:mean square displacement)。模拟结果与实验数据吻合较好,误差在10%左右。两种方法的平均值与实验结果误差在7%左右。同时还模拟了流体自扩散系数随温度的变化关系。结果表明,自扩散系数与温度满足Arrenhius关系,数据相关性在0.99以上,计算得到的自扩散激活能分别为1 258 J/mol(VACF)、1 272 J/mol(MSD)和平均值1 265 J/mol。

Molecular dynamics simulation of self-diffusion coefficient and its relation with temperature using simple Lennard-Jones potential

Diffusion coefficient is indispensable to chemical engineering design and research.However,there is great lack of such data.By the means of molecular dynamics simulation,self-diffusion coefficient for simple fluid has been simulated using Green-Kubo relation(VACF: velocity autocorrelation function) and Einstein relation(MSD: mean square displacement).The simulation results make good agreement with experimental findings except an error of about 10%. And,the average of simulation results of the two methods(average) reduces the error to 7%.The relation of diffusion coefficient with temperature has also been simulated.According to simulation results,whose correlation is all above 0.99,diffusion coefficient agrees well with temperature following Arrenhius relation.Activation energy for self-diffusion has been calculated and the results are 1 258 J/mol(VACF),1 272 J/mol(MSD) and 1 265 J/mol(average) separately.