One-dimensional analysis of the theory of dense fluids

Abstract

A simple reduction of realistic three-dimensional model systems to an approximately equivalent one-dimensional form is proposed. This reduction is then applied to the standard Lennard-Jones model of the simple fluid and isotherms are obtained from three approximate theories. The first two correspond to the Barker-Henderson and Andersen-Chandler-Weeks repulsive reference system perturbation theories and the third is a perturbation theory based on the exactly solvable nearest neighbour model. Comparison of the three theories in the liquid region is used as a preliminary investigation into the importance of correlations due to attractive forces. The same reduction is then used in the development of a new isobaric cell theory. This theory eliminates some of the major sources of error in traditional cell theories. Comparison with experimental isotherms for argon shows good agreement. The new theory does not predict condensation but, through a mechanism of Landau phase mixing, reproduces the flat parts of the isotherms to a good approximation.