Effect of ion radii and electronegativities of atoms on crystal structure type of compounds of AΛ2BΛ2OΛ7 composition

Compounds of the oxygen octahedral-type with the general A2B2O7 formula are crystallized in pyrochlore, laminated perovskite-type, weber, flouorite, of the La3NbO7-type and zirconolite structures. Effect of relations between ion radii of A and B cations and atom electronegativities on the type of the crystalline structure of A2B2O7 compounds for 733 substances known in literature is studied to establish criteria for existence of the above structures. Quantitative relations are established, which allow to forecast the structure of these compounds and their solid solutions by chemical composition, and their solid solutions by chemical composition, which may be used to synthesize substances with the given physicochemical properties