Figure 7.
Electric potential ϕ as a function of the distance from the charged planar surface x (rσ = 0) within the Stern model (Equation (77)), the SLPB model for point-like ions (Equation (79)), the SLB model for finite-sized ions (Equation (81)) and the SLB model with a step function for finite-sized ions (Equation (83)) for c = 0, where in all four cases the distance of closest approach b = a/2 = ns−1/3/2 ≈ 0.16 nm was taken into account. The value of the surface charge density was considered to be: σ = −0.2 As/m2 (upper figure) and σ = −0.4 As/m2 (lower figure). The remaining parameters used are dipole moment of water, p0 = 4.794 D; bulk concentration of salt, n0/Na = 0.15 mol/1 and bulk concentration of water, n0w/Na = 55 mol/1, where Na is Avogadro number.