Binary Collision Dynamics and Numerical Evaluation of Dilute Gas Transport Properties for Potentials with Multiple Extrema

Prediction of gaseous transport properties requires calculation of Chapman-Enskog collision integrals which depend on all possible binary collision trajectories. The interparticle potential is required as input, and for a variety of applications involving monatomic gases the Hulburt-Hirschfelder potential is useful since it is determined entirely from spectroscopic information and can accomodate the long-range maxima and minima found in many systems. Hulburt-Hirschfelder potentials are classified into five distinct types according to their qualitative binary collision dynamics, which in general can be quite complex and can exhibit “double orbiting”, i.e., a pair of orbiting impact parameters for a single energy of collision. The collision integral program of O'Hara and Smith has been revised extensively to accomodate all physical cases of the Hulburt-Hirschfelder potential, and the required numerical methods are described and justified. The revised program substantially extends the range of potentials for which collision integrals can be calculated.