Theory and simulation for associating fluids with four bonding sites

ISSN： 1362-3028

Source： Molecular Physics, Vol.79, Iss.2, 1993-06, pp. : 291-311

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Abstract

In this paper we present new results from molecular simulation and theory for associating hard spheres and Lennard-Jones (LJ) spheres with four association or hydrogen-bonding sites. The association interaction is modelled with a highly anisotropic square well. Results from the first-order perturbation form of Wertheim's theory are compared with simulation results. The agreement between simulation and theory for compressibility factor, configurational energy, fraction of monomers, and bonding distribution is good. We also obtained the cluster size distribution and the average cluster size from simulation. An expression based on the assumptions of the theory and statistical arguments was developed for the average cluster size. The agreement between simulation and this equation for average cluster size is good for small and moderate strengths of the association potential. Finally the vapour-liquid coexistence curves for associating LJ fluids were obtained from theory.