Crystal chemistry of AB 2X 4 (X = S, Se, Te) compounds

An attempt is made to correlate the crystal structures of ternary chalcogenides of composition AB ₂X ₄ with the cationic radius ratio and a pseudo force-constant involving their electronegativities. The resultant diagram adequately resolves structures based on the types K ₂SO ₄, monoclinic, olivine, MnY ₂S ₄, Th ₃P ₄, and CaFe ₂O ₄ but structure types based on spinel, Cr ₃Se ₄, and Ag ₂HgI ₄ are not resolved. Crystal chemical arguments are used to explain these observations and to advance reasons for the successes and failures of this method for predicting structure types.