Reactive Molecular Dynamics in Ionic Liquids: A Review of Simulation Techniques and Applications

Ionic liquids exhibit distinctive solvation and reactive properties, making them highly relevant for applications in energy storage, catalysis, and CO₂ capture. However, their complex molecular interactions, including proton transfer and physisorption/chemisorption, necessitate advanced computational efforts to model them at the atomic scale. This review examines key molecular dynamics approaches for simulating ionic liquid reactivity, including quantum-mechanical methods, conventional reactive force fields such as ReaxFF, and fractional force fields employed in PROTEX. The strengths and limitations of each method are assessed within the context of ionic liquid simulations. While quantum-mechanical simulations provide detailed electronic insights, their high computational cost restricts system size and simulation timescales. Reactive force fields enable bond breaking and formation in larger systems but require extensive parameterization. These approaches are well suited for investigating reaction pathways influenced by the local environment, which can also be partially addressed using multiscale simulations. Fractional force fields offer an efficient alternative for simulating significantly larger reactive systems over extended timescales. Instead of resolving individual reaction mechanisms in full detail, they incorporate reaction probabilities to model complex coupled reactions. This approach enables the study of macroscopic properties, such as conductivity and viscosity, as well as proton transport mechanisms like the Grotthuß process—phenomena that remain inaccessible to other computational methods.