DYNAMIC SIMULATION OF DIFFUSION IN DENSE FLUIDS.

A binary mixture of rigid polyatomics of different symmetry (benzene and carbon dioxide) has been studied via molecular dynamics. The kinematics of the polyatomics under study required the implementation of different algorithms for the numerical integration of the classical equations of motion. A self-consistent method (the Slater-Kirkwood equation) was used to calculate the parameters for the 12-6 site-site potential energy functions. The important electrostatic contribution to the effective intermolecular potential of CO//2 was not adequately represented by these parameters. The problem of describing the force field for CO//2 molecules, without the use of adjustable parameters, remains unsolved. Electrostatic effects introduce stiffness into the numerical problem, requiring the implementation of a higher order integration algorithm than the second order scheme considered here. Velocity distribution functions for the 107 solvent molecules were calculated by averaging over ca. 70 instantaneous phase-space configurations.