with Boltzmann constant k B , absolute temperature T , elementary charge e, valency of the ions z = |z -| = z + , salt number density ρ s = ρ + = ρ -, where ρ + and ρ -denote the corresponding densities of the ion species, and individual cation and anion self-diffusion coefficients D + and D -, respectively. The self-diffusion coefficient can be computed by