Structural investigations in the system Ga0.5V2S4-Ga0.5V2Se4

The system Ga0.5V2S4-Ga0.5V2Se4 has been investigated by powder X-ray diffr action methods. A complete series of mixed crystals with a spinel structure with 1:1 ordering on the tetrahedral sites (space group F (4) over bar 3m) is formed. The lattice parameters of the cubic cell of the mixed crystals are linearly dependent on the S:Se ratio. The structures of the two border and one intermediate compound have been solved by the Rietveld method. Frac tional parameters and interatomic distances are given for the different com positions. In the structure, the vanadium atoms are shifted from their idea l position to form isolated tetrahedral clusters with relatively short vana dium-vanadium distances of 288-296 pm. (C) 2001 Elsevier Science Ltd. All r ights reserved.