Determination of conduction paths of semiconducting electrons by bond-valence calculations

An accuracy of 0.01 Angstrom or better of experimentally determined bond lengths suggests that calculated bond valences higher than 0.06 v.u. are to be considered as representing chemical bonds, and that bond-valence sums are a measure of the effective valence of an atom. Consequently, bond valences and effective atom valences, which can easily be calculated on small personal computers, give information on the electronic structure from which conduction paths can be derived even for chemically and structurally complicated materials. Application of the method to eight semiconducting cetineite-type phases, A(6)[Sb12O18][SbX3](2)[DxY6-y], With A = Na+, K+, Rb+, Sr2+, Ba2+; X = S2-, Se2-; D = Na+, Sb3+, C4+; Y = H2O, ON-, O2-, reveals conduction paths in agreement with experimental observations and sophisticated ab initio calculations.