DYNAMICAL PROPERTIES OF CARBONYL SULFIDE DILUTED IN ARGON AT DIFFERENT DENSITIES - A MOLECULAR-DYNAMICS INVESTIGATION

Molecular dynamics simulation was used to study the single molecule dy namical properties of OCS diluted in argon at two temperatures and at different densities, The translational motion of OCS molecules was stu died by calculating the linear velocity and the center-of-mass total f orce autocorrelation functions (ACFs). The rotational motion was studi ed in terms of the angular velocity and of the first and second order reorientational ACFs. The characteristic density dependence of both mo lecular motions of OCS perturbed by argon has been obtained and discus sed in terms of the alternations in the shape of the ACFs. We found th at the best trial function which reproduces quite satisfactory the lin ear and angular velocity ACFs at low and intermediate densities is one of two exponential terms with slowly decaying tails. Gordon's general ized diffusion models as well as the ''Gaussian'' cage model were used to analyse the rotational C-omega,(t), C-1(t) and C-2(t) ACFs of OCS in argon from low to sufficiently high densities. We found that the mo st successful model in reproducing the MD rotational ACFs and especial ly in the sufficiently high density range, was the ''Gaussian'' cage m odel. Finally, this study has shown that the simulated first order reo rientational ACFs are in successful agreement with the corresponding e xperimental ACFs obtained from the fundamental parallel bands of OCS i n previous infrared studies of this molecular system.