Computed and measured thermal diffusion factor for CO-He mixtures: a test of recent interaction potentials

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Abstract
Several anisotropic interaction potentials which describe the He–CO gaseous mixture were tested via the detailed analysis of recently measured thermal diffusion factors, as functions of both temperature and concentration. The calculations were carried out using the quantum treatment of collision dynamics via the infinite order sudden (IOS) coupling scheme between angular momenta, and further using two additional schemes of approximation to second order: the Chapman–Cowling and the Kihara expansions. The results made it possible to test the relative behaviour of the repulsive regions of the various interactions examined in this work, among which those given by the density functional approach for describing van der Waals forces turn out to give fairly realistic values for the anisotropy of the repulsive wall, but have difficulties in generating the well region correctly. These new calculations confirm also the reliability of an earlier multiproperty potential when treating transport properties at temperatures above 100 K, and therefore when examining features which do not depend much on the details of the attractive well.