FLUIDS AND FLUID MIXTURES CONTAINING SQUARE-WELL DIATOMICS - EQUATIONS OF STATE AND CANONICAL MOLECULAR-DYNAMICS SIMULATION

We present new perturbation theory equations of state for square-well dimer fluids, square-well dimer mixtures, square-well dimer/monomer mi xtures and square-well heteronuclear dumbbell fluids, Our first-and se cond-order perturbation terms are based on Barker and Henderson's loca l compressibility approximation and Chang and Sandler's perturbation t heory, respectively. The perturbation approach requires knowledge of t he radial distribution functions of the reference hard-dimer fluid and hard dimer/monomer mixture, which are obtained from molecular dynamic s simulation. For mixtures we use one fluid mixing rules to approximat e the average mixture structure and perturbation parameters. The predi ctions of the perturbation theory are compared to the compressibility factors obtained from discontinuous canonical molecular dynamics simul ation, an adaptation of Anderson's canonical ensemble molecular dynami cs method to the case in which the potential is discontinuous. (C) 199 7 American Institute uf Physics.