ON THE CLOSELY-RELATED STRUCTURES OF SIF4 AND CUAL2

It is shown that the arrays formed by the majority component atoms in the structure types of SiF4 and CuAl2 are topologically equivalent and can be transformed into each other by a simple distortion of their ba sis clusters. The geometrical flexibility of the CuAl2 type is investi gated and a structure map for the representatives of this structure ty pe, as well as those of its derivatives BaFe2S4, TlSe, and U3Si, is pr esented. It is suggested that the compounds BaTe2 and SrS2 should not be counted as representatives of the CuAl2 type but form their own str ucture type. (C) 1997 Academic Press.