Force field effect on the MC prediction of vapor-liquid phase equilibria for low aliphatic alcohols

Materials like alcohols have great theoretical and experimental interests because of their tendencies to form hydrogen bond networks. The simulation of the phase equilibriua of pure substances from atomistic and molecular information is receiving increasing attention not only due to rapid development of fast computer but also because of its high ability for prediction of thermodynamic properties. In a simulation technique, the accuracy of the predicted equilibrium properties depends largely on the type of pair potential functions and their parameter sets (force field) that describe interactions between the encountered molecules. Various models have been developed to study structural and thermodynamic properties of alcohols. TraPPE force field parameters have been obtained by fitting to critical properties and saturated liquid densities of alkanes and then developed for alcohols [1]. OPLS force field introduced with the parameters have been optimized by fitting to liquid densities, heat of vaporization and liquid structure of several alkanes and then extended to liquid alcohols [2]. In this work we present the simulation results of united-atom versions of these two potentials to compare their ability for prediction of equilibrium properties of short chain alcohols over a wide range of temperature.