Density dependence of the structural properties and translational diffusion of carbonyl sulphide diluted in monoatomic solvents. A molecular dynamics investigation

We report a study of the intermolecular structure and translational diffusion of Carbonyl Sulphide (OCS) dissolved in Ne and Kr, using Molecular Dynamics (MD) simulation. The mixtures have been investigated at different thermodynamic points corresponding to the pressures between 5 and 300 bar and at temperature of 293 K. The computations were carried out with effective site-site Lennard-Jones (LJ) potential model. We found that the proposed model predicts a non-linear T-shaped dimer structure of Ne-OCS and Kr-OCS in accordance with experiment. The study of the local structure of the solute-solvents was based upon the calculated relevant pair distribution functions. The self-diffusion coefficients of both components in the mixtures were calculated and compared. The results show a non-linear dependence in the density range under study. In the case of Kr as solvent and at the whole density range under study, the diffusion coefficient of Kr appears to be larger than that of OCS. This unusual result on the solute-solvent diffusivities (m_OCS < m_Kr, D_OCS < D_Kr) has been further discussed in terms of the microscopic dynamics of the species.