The effects on the properties of transition metal carbides and nitrides produced by metal sublattice doping have been studied for quite an extended period. So far, large groups of ternary (and more complex) carbide and nitride alloys of the MxM1−x(C,N) type, where M, M are metals, have been synthesised (see Goldschmidt (1967) or Samsonov, Upadkhaya and Neshpor (1974)). In this chapter we review the results of researches on the electronic structure and interatomic bonding in such solid solutions.

Isolated 3d- and 4d-metal impurities in carbides and nitrides

The most studied of these so far is the electronic structure of isolated impurities of 3d- and 4d-metals in cubic carbides and nitrides of Sc, Ti, V, Zr, Nb (see Ivanovsky (1988) and Ivanovsky et al (1987a,b, 1988a,b, 1989)). They have been calculated by the LMTO–GF method.

As an example, Fig. 7.1 presents the LDOSs of 3d-metal impurities in TiC with a Bl crystal structure (Ivanovsky et al, 1988a). It is seen that the LDOSs of impurities are defined by the peculiarities of the interaction between the impurities and the matrix. The LDOSs may differ considerably for elements at the beginning and end of the d series. In the case of the ma–va subgroup d-metals, whose carbides and nitrides form homogeneous solid solutions with TiC, the shapes of the impurity LDOS and the matrix DOS are rather similar. In such ternary alloys a common valence band consisting of the nonmetal 2p-orbitals and d- and s-orbitals of both types of metal atom is formed.