M. Foroutan - Department of Physical Chemistry, Faculty of Chemistry, College of Science, University of Tehran, ۱۴۱۵۵-۶۴۵۵, Enghelab Ave., Tehran, Iran.
A. H. Jalili - National Iranian Oil Company (NIOC), Research Institute of Petroleum Industry (RIPI), Qom Road, P. O. Box ۱۸۷۴۵-۴۳۹۱, Tehran, Iran.
Z. Nikouie - Department of Physical Chemistry, Faculty of Chemistry, College of Science, University of Tehran, ۱۴۱۵۵-۶۴۵۵, Enghelab Ave., Tehran, Iran.

For evaluating the intermolecular potential energy from experimental sources there exists, in general, two independent approaches. The first approach, carried out by Barker et al. [1] involves the assumption of some specific potential function and the optimization of the parameters contained in the functions, so that experimental and calculated data come into agreement with on another. The second approach is the inversion procedure that [2] the potential energy is determined without any assumption about the intermolecular potential energy functions. In this work effective intermolecular potential energy functions for CF4 are obtained from the low of corresponding states for viscosity .the obtained results are fitted to a multiparameter MSV (Morse-Spline-Van der Waals) potential model.