A symmetry analysis of monoclinic, orthorhombic, and trigonal M3X2-type superstructures that can be formed in strongly stoichiometric MX (y) compounds with B1 structure is carried out. Channels of order-disorder transitions MX (y) -> M3X2 are determined. It is shown that, as temperature decreases, two physically admissible sequences of transformations associated with the formation of M3X2 superstructures are possible in nonstoichiometric MX (y) compounds of group IV transition metals. By an example of vanadium carbide VC (y) , it is demonstrated that orthorhombic or monoclinic V3C2 superstructures can be obtained with the formation of a nanostructure.
展开▼
