Application of static charge transfer within an ionic-liquid force field and its effect on structure and dynamics

Area of Science:

• Computational Chemistry
• Materials Science
• Physical Chemistry

Background:

• Ionic liquids (ILs) are crucial in various applications.
• Accurate simulations of ILs are essential for predicting their properties.
• Standard models often use +/-1 e for ionic charges, which may not reflect reality.

Purpose of the Study:

• To investigate the impact of linearly scaled atomic charges on IL simulations.
• To determine optimal charge scaling for accurate structural, dynamic, and energetic predictions.
• To offer a computationally feasible alternative to polarizable force fields.

Main Methods:

• Linear scaling of atomic charges in a reference potential.
• Molecular dynamics simulations of 1,3-dimethylimidazolium chloride.
• Comparison of simulation results with ab initio molecular dynamics data.

Main Results:

• Diffusion coefficients varied by four orders of magnitude with charge scaling.
• Scaled charges (e.g., +/-0.7 e) showed excellent agreement with ab initio data for radial distribution functions.
• Scaled-charge models improved agreement for cohesive energy densities compared to ab initio calculations.

Conclusions:

• Overestimating ionic charges (+/-1 e) leads to artifacts like overstructuring and slow dynamics.
• Linear charge scaling provides a more accurate and efficient simulation approach for ILs.
• Scaled-charge sets are beneficial for simulating IL properties beyond simple structure, offering an alternative to expensive polarizable models.