New and refined bond valence parameters for Te4+–F−, Te4+–S2− and Te4+–Se2− ion pairs

Abstract New and refined bond valence parameters related to ion pairs constituted of the tellurium Te4+ cation and non-oxide X n− anions (X = F, S or Se) are proposed. After a selection of specific crystalline structures, the optimization of the bond valence parameters R and b with a cutoff distance is carried out by minimizing the root mean square deviation of the Te4+ cation valence. The results are R = 1.728 Å and b = 0.622 Å with cutoff = 5.3 Å for the Te4+–F− pair and R = 2.444 Å and b = 0.387 Å with cutoff = 4.5 Å for the Te4+–S2− pair. These parameters lead to a lower dispersion of the calculated valences around the formal valence compared to that obtained with the parameters available in the literature. As for the new set related to the Te4+–Se2− pair, we find R = 2.578 Å and b = 0.296 Å with cutoff = 3.7 Å.