(377e) Continuous Fractional Component Monte Carlo: The General Biased Slow-Growth Method For Phase Equilibrium Simulations

We have recently developed an open system Monte Carlo procedure designed to overcome difficulties with insertion and deletion of molecules [1], particularly for systems involving complex molecules having specific interactions. The method utilizes gradual insertions and deletions of molecules through the use of a continuous coupling parameter and an adaptive bias potential. The method draws upon concepts from previous open system molecular dynamics and expanded ensemble Monte Carlo techniques, and we show how it can be applied within the grand canonical, Gibbs and osmotic ensembles. It is shown to yield correct results for the volumetric properties of the Lennard-Jones fluid and water as well as the phase behavior of the CO2- ethanol binary system. It is then used to compute absorption isotherms, excess molar volumes and enthalpies of absorption for CO2 and water in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The results are in quantitative agreement with experimental data.

[1] Wei Shi and Edward J. Maginn, J. Chem. Theory Comput. 2007, in press.