Fine-Tuning the Polarizable CL&Pol Force Field for the Deep Eutectic Solvent Ethaline.

Area of Science:

• Computational chemistry
• Materials science
• Soft matter physics

Background:

• Polarizable force fields are increasingly used for molecular dynamics (MD) simulations of ionic liquids and deep eutectic solvents (DESs).
• The CL&Pol force field, developed in 2019, was the first general and transferable polarizable force field for DES simulations.
• The original CL&Pol formulation exhibited issues in ethaline simulations, including artificial phase separation and overestimated nanoscale heterogeneity.

Purpose of the Study:

• To address and correct identified problems in the CL&Pol force field's original formulation.
• To improve the accuracy of MD simulations for DESs using a polarizable force field.
• To ensure the CL&Pol force field's robustness and applicability to various DES systems.

Main Methods:

• Adjusting chloride-hydroxyl radial distribution functions based on ab initio data.
• Extending the Tang-Toennis damping function for chlorides' induced dipoles.
• Comparing simulation results with the nonpolarizable CL&P force field.

Main Results:

• Corrected atomic diameter parameters to improve chloride-hydroxyl interactions, preventing artificial phase separation.
• Mitigated overpolarization of chlorides by refining induced dipole calculations, resolving issues in structure factor analysis.
• Validated the improved CL&Pol force field against ab initio data and its nonpolarizable counterpart.

Conclusions:

• The adjusted CL&Pol force field resolves critical simulation artifacts without compromising its overall robustness.
• These corrections are expected to enhance the reliability of CL&Pol for simulating a wider range of DESs.
• The study facilitates more accurate computational modeling of ionic soft matter systems.