Intermolecular Potentials for Unlike Interaction on Exp-Six Model

Abstract

The potential parameters for the unlike pairs of molecules A–He, A–Xe and Ne–Xe have been determined for the ``exp-six'' model from the temperature dependence of thermal diffusion of these gas mixtures following the method developed earlier by Srivastava and Madan. Unlike the graphical method of Srivastava and Srivastava a purely computational method has been employed here for determining the parameters α12 and ε12. First coupled values of α12 and ε12 were determined by neglecting the temperature variation of the ``g'' factor and using Kihara's first approximation formula. Then the absolute value of the ``g'' factor was calculated at a fixed temperature for various values of α12 and that value of α12 selected which gave the experimental value of the thermal diffusion factor αT. Precise value of ε12 was determined by taking into account the temperature variation of ``g.'' The values of the potential parameters α12, ε12, and (rm)12 thus obtained were found to reproduce satisfactorily the experimental data on thermal diffusion except for very low temperatures where T* is less than 1.5 and the ``exp-six'' law probably does not hold.