Atomic and vacancy ordering in nonstoichiometric carbides
Institute of Solid State Chemistry, Urals Branch of the Russian Academy of Sciences, ul. Pervomayskaya 91, Ekaterinburg, 620219, Russian Federation
An analysis of the electronic structure of highly nonctoichiometric transition-metal carbides in both ordered and disordered states is given, which explains the influence of atomic and vacancy order on the physical properties of the carbides. It is shown that the dependence of carbide properties on the arrangement of carbon atoms in the nonmetal sublattice is related to both the symmetry space group of the crystal and the symmetry of the nearest-neighbour environment of the carbide atoms. By analysing order-disorder phase transition data, experimental information on atomic and vacancy order in carbides is obtained in order to explain the nature of superstructures at high vacancy concentrations.