In this paper we present a new procedure, based on quantum/molecular (QM/MM) mechanics and molecular dynamics (MD) computer simulations, for estimating the Perturbed Hard Sphere Chain Theory (PHSCT) equation of state (EOS) parameters of a set of 14 alternative chloro-fluoro-hydrocarbons (CFH) of industrial relevance and to predict their thermophysical properties and PVT behavior. Force field and quantum-mechanical techniques were employed in molecular modeling and for the calculation of geometrical and chemico-physical parameters. The Connolly surface algorithm, corrected for quantum-mechanical effects, was used in the evaluation of molecular surfaces and volumes. From these data, the parameters of the PHSCT EOS, V* and A*, were obtained. The third parameter, E*, was calculated from extensive MD simulations under NPT conditions. The new, original method proposed in this work gives good results, is relatively inexpensive, is absolutely general and can be applied in principle to any EOS, provided the parameters have a physical meaning. The tuning of the energetic parameter to a generated data set accounts for the degree of empiricism introduced at a certain stage in the development of any EOS.