Electrostatic interactions in soft particle systems: mesoscale simulations of ionic liquids

Area of Science:

• Computational chemistry
• Materials science
• Physical chemistry

Background:

• Ionic liquids exhibit complex physicochemical properties due to sluggish dynamics and nanostructuring.
• Coarse-grained simulations offer a computationally efficient approach to study ionic liquids at larger scales.

Purpose of the Study:

• To investigate the impact of alkyl chain length and counterion type on ionic liquid properties using coarse-grained simulations.
• To analyze the microstructures, diffusion, and re-orientational dynamics of imidazolium-based ionic liquids.
• To compare the computational efficiency of different electrostatic calculation methods.

Main Methods:

• Extensive coarse-grained simulations of 1-alkyl-3-methylimidazolium ionic liquids with various counterions (Cl, [BF4], [PF6]).
• Systematic study of liquid densities, microstructures, translational diffusion, and re-orientational motion over a wide temperature range.
• Comparison of computational performance for particle-particle particle-mesh, particle-mesh Ewald, and non-uniform fast Fourier transform Ewald summation methods.

Main Results:

• Alkyl chain elongation and larger anion size decrease translational diffusion and affect re-orientational motion.
• Addition of neutral beads induces morphological transitions from dispersed to bi-continuous networks.
• Coulombic interactions are fundamental to the observed microstructures and dynamics.

Conclusions:

• Coarse-grained simulations are effective for understanding ionic liquid behavior across length and time scales.
• Ionic liquid properties are intrinsically linked to electrostatic interactions and molecular structure.
• Efficient electrostatic calculation methods are crucial for large-scale simulations of ionic liquids.