Influence of Polarization on Structural, Thermodynamic, and Dynamic Properties of Ionic Liquids Obtained from Molecular Dynamics Simulations

Utilizing the transferable, quantum-chemistry-based, Atomistic Polarizable Potential for Liquids, Electrolytes, & Polymers (APPLE&P) force field, we have systematically investigated the influence of polarization effects on the accuracy of properties predicted from molecular dynamics simulations of various room temperature ionic liquids (ILs). Simulations of ILs in which the atom-based polarizability was set to zero for all atoms (nonpolarizable APPLE&P potential) resulted in changes in thermodynamic and dynamic properties from those predicted by the polarizable APPLE&P potential that are qualitatively different from changes observed for nonionic liquids. Investigation of structural and dynamical correlations using both the polarizable and nonpolarizable versions of APPLE&P allowed us to obtain a mechanistic understanding of the influence of polarization on dynamics in the ILs investigated. Additionally, the Force Matching (FM) approach was employed to systematically obtain nonpolarizable two-body force fields for several ILs that reproduce as accurately as possible intermolecular forces predicted by the polarizable model. Unlike water, for which the FM approach was found to yield an accurate representation of the liquid phase structure predicted by a polarizable model, the FM approach does not result in a two-body potential that accurately reproduces either structure or dynamics predicted by the polarizable IL model.