Shear viscosity and diffusion motion of two-dimensional dusty plasma liquids

A molecular dynamics method for studying diffusion motion and shear viscosity is presented for two-dimensional (2D) plasma liquids. The calculations obtained by using the mean-squared displacement (MSD), velocity autocorrelation function (VACF) and the shear autocorrelation function indicate that there is a diffusive motion for the lower coupling range of strongly coupled liquid states. In the MSD test, both states of a transition phase from normal diffusion to superdiffusion, and the extreme superdiffusion at intermediate coupling strength are dependent on screening strengths. The simulation data show that the position of extreme superdiffusion shifts towards higher coupling with an increase in screening strength, and the superdiffusion is nearly in a constant motion for higher coupling. A smooth transition from normal diffusion to superdiffusion exhibits the existence of superdiffusion at intermediate coupling strengths in the VACF test. A valid shear viscosity exists only at the intermediate and higher coupling parameters. It seems that the present calculations cannot establish a coupling between the viscosity and diffusion in 2D Yukawa liquids.