The integrals required for the calculation of transport properties for gases are carefully examined, assuming that the intermolecular potentials vary inversely as a power of the separation, Φ = −c/rn. When the potential corresponds to mutual attraction, the behavior at the origin, corresponding to the centers of the two molecules colliding, must be prescribed because some trajectories of the relative motion reach the origin. Calculations are made on the basis of three models: (a) A rigid core corresponding to the Sutherland potential in the limit that the rigid core approaches zero (for spherical models this is the most realistic model); (b) a transparent core model which corresponds to the limiting behavior of a well-shaped potential; and (c) a random-scattering core model which is an appropriate idealization for molecules without spherical symmetry. The behavior of the collision integrals is considered for the full range of potentials as n goes from one to infinity (or from the Coulomb to the rigid-sphere potential).

Kihara, T., Taylor, M. H., & Hirschfelder, J. O. (1960). Transport Properties for Gases Assuming Inverse Power Intermolecular Potentials. The Physics of Fluids, 3(5), 715–720.