Atomistic force field for pyridinium-based ionic liquids: reliable transport properties

Area of Science:

• Computational Chemistry
• Materials Science
• Physical Chemistry

Background:

• Accurate force fields (FFs) are crucial for predicting physical chemical properties of ionic liquids (ILs) using computer simulations.
• Existing FF models may not fully capture specific cation-anion interactions in the liquid phase, limiting predictive accuracy.

Purpose of the Study:

• To develop refined FF parameters for six common pyridinium-based ILs.
• To establish a systematic procedure for accounting for cation-anion interactions in IL simulations.
• To validate the predictive capability of the refined FFs for various IL properties.

Main Methods:

• Systematic refinement of FF parameters, focusing on atom diameter, potential well depth, and electrostatic charge for each interaction site.
• Development of atomistic models based on the Canongia Lopes-Pádua (CL&P) FF framework.
• Validation against experimentally determined thermodynamics, structure, and transport properties of ILs.

Main Results:

• Refined FF parameters were developed for six pyridinium ILs, including butylpyridinium tetrafluoroborate, bis(trifluoromethanesulfonyl)imide, dicyanamide, hexafluorophosphate, triflate, and chloride.
• The refined models accurately reproduce experimentally determined transport properties (diffusion, viscosity, conductivity).
• The three-parameter approach per site sufficiently predicts thermodynamics (heat of vaporization, density) and structure (radial distributions).

Conclusions:

• The developed FF parameters provide a systematic refinement over existing models like CL&P.
• Accurate description of cation-anion interactions is key to predicting IL properties.
• These enhanced models facilitate more reliable computational investigations of ionic liquids.