Christian SCHRÖDER1, Florian JÖRG1, Steve RICK2, Johannes HUNGER3
1University of Vienna, Vienna, Austria
2University of New Orleans, New Orleans, United States
3Max-Planck-Institute for polymer research, Mainz, Germany
Although non-polarizable molecular dynamics simulations successfully modeled the structure of various ionic liquids, the simulated dynamics tend to be one order of magnitude too slow compared to the experiment. Scaled charge approaches may accelerate the dynamics at the cost of abandoning hydrogen bonding and potentially introducing simulation artifacts .
Polarizable molecular dynamics simulations are computationally more expensive but offer various advantages :
(1) The simulated dynamics usually come close to experimental data.
(2) The induced dipoles of the molecules may respond to their local environment offering new pathways which are not accessible by “fixed” charge approaches.
(3) The induced dipoles smooth the Coulomb energy in non-equilibrium events like charge and proton transfer.
Classical molecular dynamics simulations are restricted by fixed charges and the incapability to break or form new bonds. However, our novel polarizable molecular dynamics simulations include charge  and proton transfer [3-5] events, which are essential for understanding protic ionic liquids. Besides analyzing reduced charge and polarizability effects occurring simultaneously , proton transfers allow for the investigation of various conductivity mechanisms like Grotthus and vehicle transport [4,5].
 D. Bedrov, J.-P. Piquemal, O. Borodin, A. D. MacKerell Jr, B. Roux, C. Schröder “Molecular Dynamics Simulations of Ionic Liquids and Electrolytes Using Polarizable Force Fields”, Chem. Rev. 2019, 119, 7940.
 C. Schröder, A. Lyons, S. W. Rick “Polarizable MD simulations of ionic liquids: How does additional charge transfer change the dynamics”, Phys. Chem. Chem. Phys. 2020, 22, 467.
 F. Joerg, C. Schröder “Polarizable molecular dynamics simulations on the conductivity of pure 1-methylimidazolium acetate systems”, Phys. Chem. Chem. Phys. 2022, 24, 15245.
 R. Jacobi, F. Joerg, C. Schröder “Emulating proton transfer reactions in the pseudo-protic ionic liquid 1-methylimidazolium acetate”, Phys. Chem. Chem. Phys. 2022, 24, 9277.
 F. Joerg, M. Wieder, C. Schröder “PROTEX – a python utility for proton exchange in molecular dynamics simulations”, Frontiers in Chemistry, to be submitted