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

Abstract

We recently proposed that calculated bond-valence sums, BVS, represent a non-integer structural valence, `struct V', rather than the integer-value stoichiometric valence, stoich V. Therefore, the usual attempts to `optimize' bond-valence parameters r 0 and b by adjusting them to stoich V are based on the false assumption that numerical values of struct V and stoich V are always equal. Bond-valence calculations for several compounds with stereoactive cations SnII, SbIII and BiIII reveal the balanced distribution of the bonding power struct V between atoms of each structure.