8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P6.18Fri 911:10-14:00SAFT-gamma coarse grained models for the molecularsimulation of complex fluids with a top-downmethodologyGeorge Jackson, 1 Carlos Avendano, 1 Thomas Lafitte, 1 Omolara Yaroson, 1 OlgaLobanova, 1 Amparo Galindo, 1 Claire S. Adjiman, 1 and Erich A. Muller 11 Imperial College London, Chemical Engineering, South Kensington Campus SW7 2AZ,London, United KingdomWith the common “bottom-up” procedure, coarse-grained models are constructed from a suitablesimplification of a full detailed atomistic representation, and minor adjustments to theintermolecular parameters are made by comparison with limited experimental where necessary.By contrast in the top-down approach, a molecular-based equation of state is used to obtain aneffective coarse-grained intermolecular potential that reproduces the macroscopic experimentalthermophysical properties over a wide range of conditions. In order to demonstrate our procedure,coarse-grained models for carbon dioxide (CO 2 ) and alkanes are obtained from a recent implementationof the statistical associating fluid theory of variable range (SAFT-VR) employing a Mie(generalized Lennard- Jones) potential [1]. The parameters of a single-site Mie model of CO 2 anda multiple-site Mie model of the linear alkanes are estimated by optimizing the equation of state’sdescription of the experimental vapor-pressure and saturated liquid density data [2]. Our SAFTcoarse-grainedmodels for CO 2 and the n-alkanes are used in Monte Carlo molecular simulationto assess the adequacy of the description of the fluid phase behavior and properties which werenot used to develop the potential model such as the enthalpy of vaporization, interfacial tension,density profiles, supercritical densities and second-derivative thermodynamic properties. Theaccuracy of the single-site SAFT- models of CO 2 is found to be of similar quality to that of moresophisticated intermolecular potentials such as a six-site (three LJ centers and three charged sites)united atom model. The models for the alkanes also provide an accurate representation of thesystem.[1] T. Lafitte, A. Apostolakou, C. Avendaño, A. Galindo, C. S. Adjiman, E. A. Müller, andG. Jackson, submitted 2011.[2] C. Avendaño, T. Lafitte, A. Galindo, C. S. Adjiman, G. Jackson, and E. A. Müller, submitted2011.18