Equation of state of model branched alkanes: Theoretical predictions and configurational bias Monte Carlo simulations

Abstract

We develop a general configurational bias Monte Carlo algorithm for the simulation of branched alkanes and compare the results with predictions from theoretical equations of state. We consider results for all the hexane isomers, as well as for several heptane and octane isomers. The interaction sites of our united atom model alkanes are hard spheres of equal diameter, thus allowing us to study the effect of branching in the equation of state without the need of considering the effect of changes in the size of the sites. We find that, at roughly constant molecular volume, branching has a small but noticeable effect on the equation of state, somewhat reducing the pressure at which a given density may be attained. We find that equations of state previously used for linear chains yield very good agreement with simulation results.