Molecular motility and affinity of expanded carbon dioxide+ketone systems analyzed by molecular dynamics simulations

We perform a molecular dynamics simulation for CO₂+ketone mixtures to study the molecular motility and elucidate how CO₂ molecules are dissolved in a mixture. The self-diffusion coefficients increase with increasing CO₂ mole fraction (xCO2) and decreased with increasing molecular weight. These results mean that the mobility of molecules depends on the molecular size. To study molecular aggregation around CO₂ molecules, radial distribution functions (RDFs) and the distance from neighboring molecules to CO₂ molecules were calculated. The RDFs indicate that the CO₂ molecule exists near the carbonyl oxygen atom. Because of the distance of the neighboring molecule from the CO₂ molecule, the CO₂ molecule is less likely to exist around a branched alkyl ketone than a normal alkyl ketone.