Solvation Structure and Dynamics of cis- and trans-1,2 Dichloroethene Isomers in Supercritical Carbon Dioxide. A Molecular Dynamics Simulation Study.

Abstract

Molecular dynamics simulation techniques have been employed to investigate the solvation structure and dynamics in dilute mixtures of cis- and trans-1,2-dichloroethene in supercritical carbon dioxide. The calculations were performed for state points along a near-critical isotherm (1.02 T(c)) over a wide range of densities, using new developed optimized potential models for both isomers. The similarities and differences in the solvation structures around each isomer have been presented and discussed. The local density augmentation and enhancement factors of CO(2) around the isomers have been found significantly larger than the corresponding values for pure supercritical CO(2). The dynamic local density reorganization has been investigated and related to previously proposed relaxation mechanisms. The density dependence of the calculated self-diffusion coefficients has revealed the existence of a plateau in the region of 0.7-1.1 ρ(c), where the local density augmentation exhibits the maximum value. The reorientational dynamics of the C═C bond vector have been also studied, exhibiting significant differences between the two isomers in the case of the second-order Legendre time correlation functions.