SIMULATION OF HARD TRIATOMIC AND TETRATOMIC MOLECULES - A TEST OF ASSOCIATING FLUID THEORIES

Results of isothermal-isobaric Monte Carlo simulations for hard tangent homonuclear triatomic and tetratomic molecules are presented for fixed and flexible angle models. The simulation results are compared to the prediction of Wertheim's first (TPT1) and second-order (TPT2) thermodynamic perturbation theory for associating fluids and the Zhou and Stell approach. The theories are applied for hard spheres with two association sites in the limit of complete bonding. Both TPT2 and the Zhou-Stell theories produce equations of similar structure and are able to predict the density and bond angle dependence of the simulation results. Extensions of the theories to linear and branched hard chains, fused sphere molecules and mixtures are discussed and compared to new and existing simulation results.