Convergence of the hard soft sphere potential to the hard sphere potential. A molecular dynamics study of transport coefficients

Abstract

The transport coefficients of the soft sphere (SS) dense fluid are computed by molecular dynamics for increasing powers of the usual SS potential expression. It is shown that the considered transport coefficients, namely the self-diffusion, the shear and bulk viscosity coefficients, and the thermal conductivity coefficient, exhibit an asymptotic behavior for n>30, where n denotes the exponent of the SS potential inserted. A direct comparison of the velocity autocorrelation function of the hard sphere and the n=42 SS system proves the excellent agreement of both systems with respect to the dynamics. Variation of density and temperature in certain limits do not change these findings, as expected.