A Cluster Model for the Transition State and Its Study by Means of Electron Diffraction. II. Application to Some Particular Systems

In Part I of this paper a cluster model was proposed allowing to explain the geometrical features of diffuse intensity contours observed in electron diffraction patterns from binary substitutionally disordered systems. According to this model the ordering state, termed “transition state”, can be considered as being built from atomic clusters of a specific polyhedral type all satisfying a same relation, termed “cluster relation”. This relation establishes a linear relationship between the occupation operators of the cluster sites. In this paper the method is applied to the following systems and ordering models are proposed in each case: 1. The ordering of Li+ and Fe3+ ions on a f.c.c. sublattice in lithiumferrate (LiFeO2). 2. The ordering of vacancies on f.c.c. based lattices in VCx, VNx (0.70 ≦ × ≥ 0.84) and TiOx (1.05 ≦ × ≥ 1.25). 3. The ordering of vacancies on two-dimensional hexagonal lattices in FexTaS2, NixNbS2 (x ≈︁ 0.33); Ti1+xS2 (0.17 ≦ × ≥ 0.25) and in the illite mineral with Ba2+ as interlayer compensator cations.