Equation Of State For Chain Molecules Using A Site-Interaction Model - Theory, Simulation, And Correlation Of Experimental-Data

The equation of state of fluids of homonuclear square-well chains of different bond lengths is studied. The total compressibility factor is written as a sum of the hard-chain and attractive contributions. Four methods to calculate the compressibility factor for the reference hard-chain term are compared. Two methods to take into account the effect of chain length on the attractive term, the generalized Flory-dimer (GF-D) model and the ei-model, are compared. The ei-model is based on a site-site approach assuming that chain molecules are made of two kinds of segments, end and internal. The temperature and density dependence of the attractive term are taken into account by a. local composition model and by perturbation theory. The theories are tested against Monte Carlo simulations for the compressibility factor, which is obtained from simulations of fluid confined between flat plates. Good agreement is obtained in the comparisons of the theories with the simulation data. Finally, experimental vapor pressure and liquid density data are correlated using the ei-model.