MODIFIED INTERACTING-SPHERE MODEL FOR SELF-DIFFUSION AND INFINITE-DILUTION MUTUAL-DIFFUSIVITY OF N-ALKANES

The interacting-sphere (IS) model has been modified by introducing a m ultiple hard-sphere term, N, into the probability function of molecula r collisions. The new model was critically evaluated with regards to e xperimental self-diffusivities covering wide ranges of temperature and pressure. The modification corrects the probability function for mult iple hard-spheres and is particularly beneficial for n-alkanes larger than n-triaconlane. A generalized version of the modified IS model was presented and required only the carbon number in order to predict n-a lkane self-diffusivity. The new model was also used to correlate infin ite-dilution mutual-diffusivity by making use of recently published mo lecular dynamics computer results. A binary interaction parameter, cor recting interaction energy between unlike molecules, was introduced an d proven independent of temperature for a given molecular pair, but de pendent on which component was chosen to be in infinite dilution, The overall standard deviation for infinite-dilution mutual-diffusivity wa s 3.44%.