SCI和EI收录∣中国化工学会会刊

Chinese Journal of Chemical Engineering ›› 2021, Vol. 36 ›› Issue (8): 138-145.DOI: 10.1016/j.cjche.2021.04.036

• Process Systems Engineering and Process Safety • Previous Articles     Next Articles

Testing and validation of a self-diffusion coefficient model based on molecular dynamics simulations

Xia Chen1, Yan Wang2, Lianying Wu1, Weitao Zhang1, Yangdong Hu1   

  1. 1 College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China;
    2 College of Chemistry and Chemical Engineering, Qingdao University, Qingdao 266071, China
  • Received:2020-10-22 Revised:2021-04-02 Online:2021-09-30 Published:2021-08-28
  • Contact: Lianying Wu
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (21776264 and 21376231). My sincere appreciation goes to Prof. Hu and Prof. Wu who provided scientific guidance for me.

Testing and validation of a self-diffusion coefficient model based on molecular dynamics simulations

Xia Chen1, Yan Wang2, Lianying Wu1, Weitao Zhang1, Yangdong Hu1   

  1. 1 College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China;
    2 College of Chemistry and Chemical Engineering, Qingdao University, Qingdao 266071, China
  • 通讯作者: Lianying Wu
  • 基金资助:
    This work was supported by the National Natural Science Foundation of China (21776264 and 21376231). My sincere appreciation goes to Prof. Hu and Prof. Wu who provided scientific guidance for me.

Abstract: In our previous work, we endowed a new physical meaning of self-diffusion coefficient in Fick's law, which proposed that the diffusion coefficient can be described as the product of the characteristic length and the diffusion velocity. To testify this simple theory, in this work, we further investigated the underlying mechanism of the characteristic length and the diffusion velocity at the molecular level. After a complete dynamic run, the statistical average diffusion velocity and the characteristic length of molecules can be obtained by scripts, and subsequently the diffusion coefficient was determined by our proposed theory. The diffusion processes in 35 systems with a wide range of pressure and concentration variations were simulated using this model. From the simulated results, diffusion coefficients from our new model matched well with the experimental results from literatures. The total average relative deviation of predicted values with respect to the experimental results is 8.18%, indicating that the novel model is objective and rational. Compared with the traditional MSD-t model, this novel diffusion coefficient model provides more reliable results, and the theory is simple and straightforward in concept. Additionally, the effect of gas pressure and liquid concentration on the diffusion behavior were discussed, and the microscopic diffusion mechanism was elucidated through the distribution of diffusion velocity and the characteristic length analysis. Moreover, we suggested new distribution functions, providing more reliable data theoretical foundations for the future research about the diffusion coefficient.

Key words: Diffusion, Molecular simulation, Parameter identification, Characteristic length, Diffusion velocity

摘要: In our previous work, we endowed a new physical meaning of self-diffusion coefficient in Fick's law, which proposed that the diffusion coefficient can be described as the product of the characteristic length and the diffusion velocity. To testify this simple theory, in this work, we further investigated the underlying mechanism of the characteristic length and the diffusion velocity at the molecular level. After a complete dynamic run, the statistical average diffusion velocity and the characteristic length of molecules can be obtained by scripts, and subsequently the diffusion coefficient was determined by our proposed theory. The diffusion processes in 35 systems with a wide range of pressure and concentration variations were simulated using this model. From the simulated results, diffusion coefficients from our new model matched well with the experimental results from literatures. The total average relative deviation of predicted values with respect to the experimental results is 8.18%, indicating that the novel model is objective and rational. Compared with the traditional MSD-t model, this novel diffusion coefficient model provides more reliable results, and the theory is simple and straightforward in concept. Additionally, the effect of gas pressure and liquid concentration on the diffusion behavior were discussed, and the microscopic diffusion mechanism was elucidated through the distribution of diffusion velocity and the characteristic length analysis. Moreover, we suggested new distribution functions, providing more reliable data theoretical foundations for the future research about the diffusion coefficient.

关键词: Diffusion, Molecular simulation, Parameter identification, Characteristic length, Diffusion velocity