INTERMOLECULAR POTENTIALS FOR BRANCHED ALKANES AND THE VAPOR-LIQUID PHASE-EQUILIBRIA OF N-HEPTANE, 2-METHYLHEXANE, AND 3-ETHYLPENTANE

Configurational bias Monte Carlo calculations in the Gibbs ensemble ha ve been used to perform direct simulations of the vapour-liquid phase equilibria of three heptane isomers: n-heptane, 2-methylhexane, and 3- ethylpentane. The simulations were carried out using isotropic united- atom representations of the Lennard-Jones type for the CH3, CH2 and CH groups. The aim of these calculations is to extend our force field, p reviously derived for linear alkanes, to branched alkanes by fitting n ew interaction parameters for methyl and ethyl branches.