The electronic structures of MC compounds (M=3d transition metal) in NaCl, CsCl and WC phases have been investigated by using the first principle method. The calculated results indicate that, the band structures of the MC compounds in the same phase are similar, and as a result of the rigid band model, we obtained the uniform distribution of the density of states (DOS) for MC compounds in three phases. According to the DOS value near the Fermi level and the calculated cohesive energy, the relative stability for three phases can be determined. For the MC compounds in CsCl phase, it exhibits the bad phase stability. For the MC compounds of Sc～V, the most stable phase is NaCl phase, and the WC phase is suitable for the MC compounds of Cr～Ni. Moreover, the chemical bonding of MC compounds in three phases has been studied by using the two sublattice model, and their influences on the phase stability are also discussed.

Key words: transition metal carbide, phase stability, chemical bonding, band structure