Title: THE ENSKOG THEORY FOR SELF-DIFFUSION COEFFICIENTS OF SIMPLE FLUIDS WITH CONTINUOUS POTENTIALS
Author(s): K.Miyazaki (IRI, Delft University of Technology, 2629 JB Delft, The Netherlands; E-mail: K.Miyazaki@iri.tudelft.nl), G.Srinivas, B.Bagchi (Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, India; E-mail: bbagchi@sscu.iisc.ernet.in)

We develop the Enskog theory for the self-diffusion coefficient for fluids with continuous potentials. General expressions for the memory kernel and the self-diffusion coefficient are derived starting from the Green-Kubo formula. The time-dependent memory kernel is calculated and compared with molecular dynamics simulations for the Lennard-Jones fluid. Excellent agreement is obtained at low density. The self-diffusion coefficient is evaluated for several temperatures and densities. The ratio of the Enskog self-diffusion coefficient to the simulation value is plotted against density for the Lennard-Jones fluid. Significant difference of this density dependence from that for the hard-sphere fluid is observed. In particular, the well-known maximum observed in the hard-sphere fluid is found to be completely absent in the Lennard-Jones fluid.

Key words: Enskog theory, self-diffusion coefficient, Lennard-Jones fluid, memory kernel
PACS: 66.30.H, 47.10.+g