| Perfluoro compounds receive much attention due to their distinctive properties and multiple applications. Consequently, it would be of great interest to be able to model those applications with molecular simulation techniques. To achieve this goal, a realistic potential model is needed. For perfluoroalkanes, such a model has been developed and reported. However, for perfluoroethers, no such model currently exists. In this work, a realistic united atom potential model has been developed. This model is composed of a harmonic function for the bond bending potential, a 7th order polynomial function of cosine &phis; for the torsional potential, partial charge, and Columbic interaction for the long-range interaction, and Lennard-Jones potential for van der Waals interaction. This model has been shown to reproduce the phase envelope and the critical properties of the modeled molecules reasonably well. A generalized partial charge set is also suggested for perfluoro chain molecules.; Also, following previous work by Salaniwal et al. on the self-assembly of water and surfactant in super- or near-critical carbon dioxide with a di-chain surfactant having one perfluoroalkane chain, the properties of the largest aggregate in this system have been further studied. The density and pressure profiles for the aggregate have been calculated from which the interfacial tension between the aggregate and carbon dioxide has been derived. A reliable transverse pressure profile has not been calculated independently from simulation so far; however, the more straightforward normal pressure profile has. The transverse pressure profile has been obtained from the normal pressure tensor by assuming mechanical equilibrium. The normal pressure profiles for the systems with and without surfactant show qualitative difference. However, the interfacial tensions for the systems with and without surfactant derived from the normal and transverse pressure profile components are statistically insignificant. |
