Figure 2.

Ratio of the gap between the (a) third- and fourth-, (b) eighth- and ninth-, (c) thirteenth and fourteenth-shortest interatomic distance and the mean bond length of the (a) three, (b) eight, (c) thirteen shortest interatomic distances for coordination numbers (a) [3] and [4], (b) [8] and [9] and (c) [13] and [14]. Ions used are (a) Li⁺, Be²⁺, B³⁺, Na⁺ and S⁶⁺; (b) Na⁺, Ca²⁺, Y³⁺, Te⁴⁺, La³⁺; (c) K⁺, Rb⁺, Cs⁺, Ba²⁺. The lack of overlap between the two distributions of Fig. 2 ▸(a) suggests that the fourth shortest distance for ions described as [3] is non-bonding. In Figs. 2 ▸(b) and (c), the increasing overlap between the two distributions shows that the determination of the exact coordination number for larger coordination polyhedra is more ambiguous. Sample sizes are (a) n _[3] + 1 = 41 and n _[4] = 58 coordination polyhedra; (b) n _[8] + 1 = 50 and n _[9] = 50 coordination polyhedra; (c) n _[13] + 1 = 50 and n _[14] = 47 coordination polyhedra.