FIGURE 1.

Left diagram: plot of the truncated Coulomb potential $u(r)$ as a function of the radial distance $r$ according to Equation 5. The truncation distance is $r_0$ , and the Bjerrum length is $l_B$ . Right diagram: truncated Coulomb potential $u(r)$ (thick solid line) together with the increasingly more accurate approximations $u_1(r)$ (first order, shown in red color), $u_2(r)$ (second order, orange), $u_3(r)$ (third order, green), and $u_4(r)$ (fourth order, blue), as defined in Equation 8. The dotted line marks the Coulomb potential $l_B/r$ .