Viscosity of the Ionic Liquid 1-Butyl-3-Methylimidazolium Chloride [BMIM]Cl From Reverse Nonequilibrium Molecular Dynamics

Reverse nonequilibrium molecular dynamics (RNEMD) simulations were carried out to compute the shear viscosity of the pure ionic liquid mixture 1-butyl-3-methylimidazolium chloride [BMIM]Cl. The program LAMMPS was used to implement the RNEMD simulations. In order to validate the implementation of the RNEMD method argon and water systems were modeled. These simulations yielded close agreement with previous studies. [BMIM]Cl was modeled using the force field developed by Canongia Lopes and Padua (J. Phys. Chem. B 2004, 108, 2038-2047). Due to the nature of the fixed C-H bonds of the cation in this model the RNEMD algorithm was applied to non-hydrogen atoms for one set of simulations and then only the Cl anions in another set of simulations. The former simulations yielded viscosity values that were in close agreement with experimental values while the latter yielded values much larger. These results demonstrate the implementation of the RNEMD method to measure the viscosity of ionic liquid systems.