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

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 angstrom and b = 0.622 angstrom with cutoff = 5.3 angstrom for the Te4+-F- pair and R = 2.444 angstrom and b = 0.387 angstrom with cutoff = 4.5 angstrom 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 angstrom and b = 0.296 angstrom with cutoff = 3.7 angstrom.