Development of a force ®eld for molecular simulation of the phase equilibria of per ̄uoromethylpropyl ether

A ®rst step towards the development of a general, realistic potential model for per ̄uoroether compounds has been to parameterize a united atom model for a short chain per ̄uoroether per ̄uoromethylpropyl ether (CF3CF2CF2OCF3). The potential model takes the usual form in which separate bond bending and torsional terms describe the intramolecular interactions with the addition of van der Waals and electrostatic terms to describe the non-bonded interactions. Ab initio quantum calculations have been carried out to obtain the partial charges and intramolecular torsional and bending potentials. Phase equilibrium data were then used to optimize the van der Waals interaction parameters through Gibbs ensemble Monte Carlo simulations. The resulting model reproduces vapour±liquid equilibrium densities, the critical temperature and the critical density of per ̄uoromethylpropyl ether, in good agreement with those from experiment.