(2) where κ = 2en 0 /ε w ε 0 k B T is the inverse Debye screening length, n 0 is the monovalent salt concentration, ε = ε ∞ /ε w , and ε w = 80 is the dielectric constant of water. In Eq. (2), C(l, x) is the multipole coupling function as described in the Supplementary Information (SI) and in Fig. and it is important to note that it exhibits no exponential screening, so that the different multipoles in the electrostatic energy are coupled algebraically.