Accurate effective potentials and virial coefficients in real fluids. Part III.Alkanes and perfluoroalkanes

Abstract

The approximate nonconformal (ANC) theory recently proposed has been applied very successfully to the determination of interaction pair potentials for the noble gases, homodiatomics and their mixtures. The ANC theory is used here to obtain effective angle-averaged potentials of all those n-alkanes and perfluoroalkanes for which experimental second virial coefficient data are available. The effective parameters conform to theoretical models based on spherocylinders and site–site chain molecules. The critical volumes and temperatures of these gases vary smoothly when scaled with parameters of the ANC potential. Further, the ANC model with only three parameters for each substance is able to reproduce the experimental data B_exp(T) of the second virial coefficient within experimental uncertainty for all 14 gases for which B_exp(T) has been reported.