Rice-Allnatt theory: Comparison of calculated shear-viscosity and thermal-conductivity coefficients with molecular-dynamics results.

Abstract

For several liquid and fluid states of the Lennard-Jones system, the shear viscosity ${\ensuremath{\eta}}_{s}$ and the thermal conductivity \ensuremath{\lambda} were calculated with the Rice-Allnatt (RA) theory and compared with molecular-dynamics (MD) data. The pair potential was split as Weeks, Chandler, and Andersen proposed [J. Chem. Phys. 54, 5237 (1971)], the pair correlation functions were generated by the perturbation method using the Baxter technique, and the friction coefficient was obtained from MD computations with use of the Green-Kubo relation. Though sufficient agreement with MD results occurred for a certain small region of states, the RA transport coefficients generally deviated largely from the MD data. The failure of the RA theory cannot be ascribed to the uncertainty in the soft part of the friction coefficient, ${\ensuremath{\zeta}}_{s}$, necessary for the kinetic equations. We proved this for states where the product, \ensuremath{\lambda}${\ensuremath{\eta}}_{s}$, is only negligibly dependent on ${\ensuremath{\zeta}}_{s}$.