Athermal lattice chains compared with hard-sphere chains

The Guggenheim–Huggins–Miller approximation of athermal lattice fluids has been a basis for lattice fluid equations of state. For better understanding of GHM solution, it was compared with molecular simulation data of hard-sphere chains. Relations were developed between parameters of lattice and off-lattice chain fluids for the comparison. The Guggenheim–Huggins–Miller approximation was found in good agreements with molecular simulation data of fused-hard-spheres when compared using the developed relations. But the agreements of GHM solution with tangent-hard-sphere chain data were found less satisfactory and deviations increased as segment number increased. Average deviations of GHM solution from mixed tangent-hard-sphere chain data were found similar to those of pure components. Real fluid parameters fitted to a GHM-based lattice fluid equation of state and the first order thermodynamic perturbation theory-based SAFT were found optimized to give similar repulsive contributions.