MolecularDynamics Simulation of Diffusion and Structureof Some n-Alkanes in near Critical and SupercriticalCarbon Dioxide at Infinite Dilution.

The diffusion coefficients of n-alkanes (fromCH4to C14H30) in near critical andsupercritical carbon dioxide at infinite dilution have been studiedby molecular dynamics simulation. The simulation results agree wellwith experiment, which suggests that the simulation method is a powerfultool to obtain diffusion coefficients of solutes in fluids at highpressures. The local structures of such fluids are further investigatedby calculating radial distribution functions and coordination numbers.Meanwhile, the dihedral, end-to-end distance and radius of gyration,which are calculated to characterize the flexibility of n-alkanes, are used to reasonably explain the abnormal trends on radialdistribution functions and coordination numbers. Moreover, it is foundthat the flexibility effects on diffusion in pure n-alkanes and infinitely dilute n-alkane/CO2system are different. The differences in MD simulation results ofmolecular diffusion in such systems could be qualitatively explainedby the flexibility. [ABSTRACT FROM AUTHOR]