Dynamical properties of carbonyl sulphide diluted in argon at different densities. A molecular dynamics investigation Original Research Article

Molecular dynamics simulations was used to study the single molecule dynamical properties of OCS diluted in argon at two temperatures and at different densities. The translational motion of OCS molecules was studied by calculating the linear velocity and at center-of-mass total ff force autocorrelation functions (ACFs). The rotational motion was studied in terms of the angular velocity and of the first and second reorientational ACFs. The characteristics density of both molecular motions of OCS perturbed by argon has been obtained and discussed in terms of the alternaions in the shape of the ACFs. We found that the best trial function which reproduces quite satisfactory the linear and angular velocity ACFs at low and intermediate densities is one of two exponential terms with slowly decaying tails. Gordonʹs generalized diffusion models as well as the “Gaussian” cage model were used to analyse the rotational Cω(t), C1(t) and C2(t) ACFs of OCS in argon from low to suffiently high densities. We found that the most successful model in reproducing the MD rotational ACFs and especially in the sufficiently high density, was the “Gaussian” cage model. Finally, this study has shown that the simulated first order reorientational ACFs are in successful agreement with the corresponding experimental ACFs obtained from the fundamental parallel bands of OCS in previous infrared studies of this molecular system.