Field-driven Simulations to Probe the Impact of Ionic Correlations on Solution Transport Coefficients in Binary, Ternary and Reciprocal Quaternary Aqueous Electrolytes

Ionic correlations play a critical role in governing ion transport properties of aqueous systems, yet their quantitative characterization remains challenging, particularly for multicomponent systems. In this work, we develop a generalizable non-equilibrium molecular dynamics framework to efficiently compute Onsager transport coefficients (ionic correlations), conductivity, and salt diffusivity in mixed-salt aqueous solutions. Specifically, using field-driven simulations, we obtain accurate Onsager matrices for LiCl/KCl, KCl/KBr, and LiBr/KCl electrolyte solutions with both improved precision and reduced computational cost relative to common equilibrium Green-Kubo methods. This framework enables direct assessment of how attractive cation-anion and repulsive cation-cation/anion-anion interactions contribute to conductivity and salt diffusivity across compositions at constant total ionic concentration. While static ion pairing exhibits strong composition dependence, ionic correlation contributions remain nearly invariant, leading to constant deviations from Nernst-Einstein conductivity predictions. These results highlight the disconnect between static ion association and dynamic transport correlations, and they establish a transferable approach for analyzing ion transport in complex electrolyte environments relevant to separation processes and electrochemical systems.