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本文首先通过采用Green-Kubo自相关函数和平衡法对简单流体Ar的扩散系数、黏度以及导热系数等输运参数进行了分子动力学模拟,发现利用平衡分子动力学模拟方法求解流体输运特性时在一定时长后会出现波动很大的现象,进而对这一现象进行了深入的探讨,发现这是利用分子动力学模拟方法对自相关函数积分求解流体输运热物性时本身就存在的问题。通过研究发现单位时长引入的误差、不同时长统计步数、系统模拟步数、不同系综的采用以及Green-Kubo方程本身都会对最终的结果产生影响;其中影响最大的是单位时长引入的误差。最后还给出了在不同系综和统计步数下黏度和导热系数的模拟值,与实验值吻合较好。
In this paper, the molecular dynamics simulations of diffusion coefficient, viscosity and thermal conductivity of simple fluid Ar were carried out by using Green-Kubo auto-correlation function and equilibrium method. It was found that when using equilibrium molecular dynamics simulation to solve the fluid transport characteristics After a certain period of time there will be a great fluctuation, and then this phenomenon has been discussed in depth. It is found that this is the use of molecular dynamics simulation method for the autocorrelation function integral solution of thermal transport properties of fluid itself problems. The results show that the error introduced per unit time, the number of statistical steps of different durations, the number of system simulation steps, the use of different ensembles and the Green-Kubo equation itself all have an impact on the final results. The most significant one is the error introduced per unit time. Finally, the simulation values of viscosity and thermal conductivity under different ensemble and statistical steps are given, which are in good agreement with the experimental data.