For the last two decades ionic liquids (ILs) have been explored for a wide range of possible applications including as solvents for organic chemistry, electrolytes for batteries, and as carbon capture materials. Understanding these ILs at a molecular level would help to elucidate the mechanisms of these processes, and this understanding can be facilitated through the use of Molecular Dynamics (MD) simulations. Those running MD simulations of ILs must normally choose between the use of polarizable force fields and non-polarizable (often charge scaled) force fields. While the non-polarizable force fields are often much less expensive, they are also less accurate and less transferrable. The MD package OpenMM can use GPU acceleration of Langevin dynamics to achieve acceptable computational time to simulation time ratios for polarizable ionic liquids force fields. However, temperature control in MD is well known to alter time dependent properties. Recent work has shown that this can be mitigated by using a sufficiently small Langevin bath coupling constant. A polarizable force field was used to calculate the bulk transport properties of a number of ILs in 100 ns MD simulations run using Langevin dynamics with varied coupling constants. These transport properties were compared to other molecular dynamics simulations and experimentally determined values for the ILs.

Transport properties of ionic liquids determined from molecular dynamics simulations with polarizable force fields

ACS Fall 2021

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