Different cations occupy filter binding sites with different propensity. (A and B) Probability density profiles for K⁺ (dark blue), Rb⁺ (red), and Cs⁺ (orange) in SF at −250 mV (A) and −500 mV (B). The density profiles were computed as kernel density estimates for aggregated simulations at both voltages. (C) Boxplots depicting the dwell time of K⁺/Cs⁺ in SF sites at −500 mV. Boxes span the interquartile range between Q1 and Q3, whiskers denote the 1.5 interquartile distance, while outliers are shown as single points. SF positions were assigned using filtered ion trajectories (see Materials and methods). Data shown in A and B were obtained from simulations conducted with pure solvated KCl (n = 3 at −250 mV, n = 4 at −500 mV), RbCl (n = 3 at −250/−500 mV), and CsCl (n = 2 at 250 mV, n = 3 at −500 mV), with a simulation time of 500 ns each. Results for C were obtained from simulations with KCl and mixed KCl/CsCl at −500 mV (n = 4 for both).