A new analytical perturbed equation of state for hard chain fluids with attractive potentials of variable range

A completely analytical perturbation theory equation of state for hard chain fluids is derived. The derived equation of state can represent the thermodynamic properties of many kinds of hard chain fluids such as the square-well chain and Yukawa chain fluid, by varying of its parameters. The predicted results are in good agreement with both the molecular simulation data and the well-known equations of state. In this paper the hard chain molecules are modelled as a pearl necklace of freely jointed spheres that interact via site-site intermolecular potential. Our first- and second-order perturbation terms are based on the Barker-Henderson local compressibility approximation and Gulati-Hall's perturbation theory, respectively. To obtain the perturbation terms, we do not require knowledge of site-site radial distribution function of the reference hard chain fluid, which is obtained from molecular dynamic simulation, or any explicit mathematical form of it. This perturbation method yields a simple and general analytical expression for each thermodynamic property of hard chain fluids. The most important feature of this equation of state is that it has no adjustable parameters and in some regions in which there is no simulation data for such fluids, such equation may be used to predict the needed data.