On the optimization of bond-valence parameters: artifacts conceal chemical effects

We recently proposed that calculated bond-valence sums, BVS, represent a non-integer structural valence, `<sup>struct</sup>V', rather than the integer-value stoichiometric valence, <sup>stoich</sup>V. Therefore, the usual attempts to `optimize' bond-valence parameters r₀ and b by adjusting them to ^stoichV are based on the false assumption that numerical values of ^structV and ^stoichV are always equal. Bond-valence calculations for several compounds with stereoactive cations Sn^II, Sb^III and Bi^III reveal the balanced distribution of the bonding power ^structV between atoms of each structure.