Role of Viscosity in Deviations from the Nernst-Einstein Relation

Deviations from the Nernst-Einstein rela- tion are commonly attributed to ion-ion (cross)correlation and ion-pairing. Despite the fact that these deviations can be quantified by either experimental measurements or molecular dynamics simulations, there is no rule of thumb to tell the extent of deviations. Here, we show that deviations from the Nernst-Einstein relation scale linearly with the inverse viscosity by exploring the finite-size effect in periodic boundary conditions. This conclusion is in accord with published experimental results of ionic liquids.