Calculating thermodynamic properties of an ionic liquid with Monte Carlo simulations with an orthorhombic and a cubic simulation box.

In contrast to the common usage of cubic simulation boxes, in this work simulations of the ionic liquid 1-n-butyl-3-methyl-imidazolium hexafluorophosphate ([bmim][PF(6)]) were carried out in a dynamic orthorhombic simulation box over a temperature range from 313 to 373 K in a canonical harmonical simulation ensemble (NpT) with a united-atom potential based on quantum chemistry. The solubilities of the gases CO(2), CO, H(2), O(2), C(2)H(4), and H(2)O at infinite dilution were determined by means of the Widom test particle method; the results are compared with experimental data and simulation results obtained with a cubic simulation box. For gas potentials containing partial charges the results are in good agreement with the experimental data.