Counting the number of cations in the pore. (A and B) Schematic representation of cylinder-shaped zones for counting the number of cations within the pore (A) and count density distribution underlying CDF plot in Fig. 2 D (B). The three zones encompassing Sa (p23), Sb (p34), as well as S3 and the zone corresponding to the vestibule, are separately marked as SF* and ves., respectively.