Comparison of the Accuracy and the Efficiency among Different Molecular Dynamics Methods for Calculating the Viscosity

Institute of Mechanical and Automotive Engineering, South China University of Technology, No. 381 Wushan Road, Tianhe District, Guangzhou 510640, China

Abstract

The viscosity is one of the important parameters which determine the characteristics of the fluid flow. In this paper, we employed three molecular dynamics methods so-called the periodic poiseuille flow method, the shear flow method and the stress autocorrelation method to calculate the viscosity of the Lennard-Jones fluid. We have found that, among the three, the periodic poiseuille flow method has the greatest convergent speed and the highest accuracy; the shear flow method with a small shear rate has the smallest convergent speed. The accuracy of the stress autocorrelation method evidently depends on the computational time. With 10⁵ time-steps it is as accurate as the shear flow method, but with double time-steps it is more accurate than the shear flow method.