Density Functional Theory and Computer Simulation for Associating Cyclic Molecules

A density functional theory for associating cyclic molecules is presented in the framework of Wertheim’s thermodynamic perturbation theory.  The theory provides results for the microstructure of the fluid confined in a slit pore, as well as accurate estimates for properties of the bulk fluid.  The models derived from this theory will be useful in describing carboxylic acid and similar systems.

In this study, we have chosen a fluid of cyclic molecules of three tangent hard spheres with one association site.  Density profiles for the fluid next to a hard wall are presented.  Metropolis Monte Carlo simulations were performed and compared very favorably to the theory results.  The theory requires the determination of the probability for association as a function of distance from the wall (K parameter) which was determined via computer calculations.