Hydrodynamic Interactions in Ion Transport -- Theory and Simulation

Abstract

We present a hydrodynamic theory describing pair diffusion in systems with periodic boundary conditions, thereby generalizing earlier work on self-diffusion [Dünweg and Kremer, J. Chem. Phys. 1993, 99, 6983-6997; Yeh and Hummer, J. Phys. Chem. B 2004, 108, 15873-15879]. Its predictions are compared to Molecular Dynamics simulations for a liquid carbonate electrolyte and two ionic liquids, for which we characterize the correlated motion between distinct ions. Overall, we observe good agreement between theory and simulation data, highlighting that hydrodynamic interactions universally dictate ion correlations. However, when summing over all ion pairs in the system to obtain the cross-contributions to the total cationic or anionic conductivity, the hydrodynamic interactions between ions with like and unlike charges largely cancel. Consequently, significant conductivity contributions only arise from deviations from a hydrodynamic flow field of an ideal fluid, that is, from the local electrolyte structure as well as from relaxation processes in the subdiffusive regime. In case of ionic liquids, the momentum-conservation constraint additionally is vital, which we study by employing different ionic masses in the simulations. Our formalism will likely also be helpful to estimate finite-size effects of the conductivity or of Maxwell-Stefan diffusivities in simulations.

References in corpus (7)

• Correlations from ion-pairing and the Nernst-Einstein equation
• Molecular theories and simulation of ions and polar molecules in water
• On finite-size effects in computer simulations using the Ewald potential
• Systematic errors in diffusion coefficients from long-time molecular dynamics simulations at constant pressure
• Local volume conservation in concentrated electrolytes is governing charge transport in electric fields
• Pair diffusion, hydrodynamic interactions, and available volume in dense fluids
• Controlling ${\text{Li}}^{+}$ transport in ionic liquid electrolytes through salt content and anion asymmetry: A mechanistic understanding gained from molecular dynamics simulations

Cited by in corpus (1)

• Bridging Electrostatic Screening and Ion Transport in Lithium Salt-Doped Ionic Liquids