The orientational correlation times for the single particle and the collective second rank Legendre polynomial are calculated for a dense fluid using Enskog kinetic theory. The rotating molecules are modeled as smooth spherocylinders and rough spheres. For rough sphere molecules, the dynamic part of the collective orientational timej2is sensitive to anisotropies in the contact radial distribution function (rdf). Spherocylinder models exhibit dynamic as well as static contributions toj2in thatj2minus;1 is nonzero even if the rdf is isotropic. Like the smooth ellipsoid models, orientational correlation times derived from Enskog theory underestimate the friction on a molecule rotating in a liquid. Predictions of kinetic theory agree best with the results from molecular dynamics on smooth, hard spherocylinders.
展开▼
