Comparing reduced partial charge models with polarizable simulations of ionic liquids

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Materials Science

Background:

• Molecular ionic liquids exhibit strong electrostatic interactions, influencing their structure and dynamics.
• Classical molecular dynamics (MD) simulations can overestimate these interactions, leading to inaccurate predictions.
• Accurate simulation of ionic liquids is crucial for understanding their properties and applications.

Purpose of the Study:

• To compare the impact of charge-scaled models versus polarizable force fields on the structure and dynamics of molecular ionic liquids.
• To investigate whether charge-scaled models adequately account for polarizability effects in MD simulations.
• To analyze simulation results at atomic, molecular, and collective levels.

Main Methods:

• Performed multiple molecular dynamics simulations of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate.
• Employed varying levels of polarization (e.g., Drude-oscillators) and charge scaling factors (0.74-0.90 e).
• Analyzed structural and dynamical properties across different scales, from atomic to collective behavior.

Main Results:

• Charge-scaled models and polarizable force fields yield different structural and dynamical outcomes for molecular ionic liquids.
• The degree of charge scaling impacts the simulation results, affecting translational and rotational behavior.
• Analysis revealed distinct differences at atomic, molecular, and collective levels between the simulation approaches.

Conclusions:

• The choice of simulation model (charge-scaled vs. polarizable) significantly influences the predicted structure and dynamics of molecular ionic liquids.
• Charge-scaled models may not fully replicate the effects of polarizability captured by more sophisticated methods.
• Further research is needed to determine the optimal simulation strategy for accurately modeling molecular ionic liquids.