Deciphering Ball Milling Mechanochemistry via Molecular Simulations of Collision‐Driven and Liquid‐Assisted Reactivity

Abstract Mechanochemistry by ball milling proceeds through a series of discrete, high‐energy collisions between milling balls and the sample, yet the molecular‐level processes that govern the resulting chemical and physical transformations remain poorly understood. In this study, we develop a molecular dynamics simulation protocol to investigate a model mechanochemical reaction between potassium chloride (KCl) and 18‐crown‐6 ether, both under dry conditions and in the presence of water as a liquid additive. Our simulations reveal that the reaction is initiated by collision‐induced fragmentation of the KCl crystal into individual ions. This process occurs when the absorbed energy per ion pair during a collision exceeds the crystal's cohesion energy. We further show that the addition of a small amount of water facilitates the formation of complexes between potassium ions and 18‐crown‐6 molecules. However, excessive water content stabilizes the reactants instead, thereby suppressing complex formation. These findings highlight a non‐linear relationship between liquid additive concentration and the reaction outcome. Our approach offers a molecular‐level perspective on mechanochemical reactivity, providing valuable insights that could guide the rational optimization of milling conditions—particularly the targeted selection and dosing of liquid additives—to improve reaction efficiency.