IMPROVED RESULTS FOR THE POTENTIAL PARAMETERS OF METHYL AND METHYLENEOBTAINED FROM 2ND VIRIAL-COEFFICIENTS OF N-ALKANES

Second virial coefficients of n-alkanes have been evaluated using the rotational isomeric state model. Methyl and methylene groups have been modelled as Lennard-Jones (12-6) sites differing in size and in energ y well depth. The parameters have been chosen to reproduce experimenta l values of second virial coefficients of a number of n-alkanes in a b road range of temperatures. The new proposed parameters improve the de scription of the experimental data with respect to our previous work ( Lopez Rodriguez, A., Vega, C., Freire, J. J., and Lago, S., 1991, Mole c. Phys., 73, 691). Moreover, differences in the fitted size and well depth of the methyl and methylene groups appear now as physically reas onable.