Structural Features of Binary Mixtures of Supercritical CO2 with Polar Entrainers by Molecular Dynamics Simulation

Computer simulations of supercritical carbon dioxide and its mixtures with polar cosolvents: water, methanol, and ethanol (concentration, 0.125 mole fractions) at T = 318 K and. = 0.7 g/cm(3) are performed. Atom-atom radial distribution functions are calculated by classical molecular dynamics, while the probability distributions of relative orientation of CO2 molecules in the first and second coordination spheres describing the geometry of the nearest environment of CO2 molecules and the trajectories of cosolvent molecules are found using Car-Parrinello molecular dynamics. Based on the latter, the conclusions regarding structure and interactions of polar entrainers in their mixtures with supercritical CO2 are made. It is shown that the microstructure of carbon dioxide varies only slightly upon the introduction of cosolvents.