Modeling Diffusion in Deep Eutectic Solvents Using a Charge-scaled Polarizable Force Field

Accurate modeling of self-diffusivity in deep eutectic solvents (DESs) is critical for understanding mass transport in electrochemical and separation applications. However, the complex hydrogen-bonding networks and heterogeneous charge distributions in DESs present major challenges for molecular simulations. We investigated translational self- diffusion in five choline chloride–based DESs using the polarizable AMOEBA force field with targeted monopole scaling, validated against quantum mechanics and experiments. Although AMOEBA’s explicit polarization captured key features of DES hydrogen- bond networks, quantitative agreement with experiment required charge scaling. For non-hydroxyl DESs, excellent agreement was achieved by scaling only the monopoles of choline chloride by +10%, whereas hydroxyl-rich DESs required uniform –10% scaling of ions and hydrogen bond donors to capture stronger hydrogen bonding and polyhydroxyl differences. AMOEBA thereby captures the influence of donor identity on diffusivity. Structural properties are also well reproduced. These findings establish a transferable modeling strategy and provide benchmarks for future polarizable force fields.