First-principles study of thermodynamic and stability properties of TiC-SiC alloys

The total energy, formation energy, phonon spectra and thermodynamical characteristics of B1-SixTi1- xC alloys were investigated as functions of composition using an ab initio pseudo-potential method. Spinodal and binodal decompositions of the alloys into cubic domains take place over a wide range of compositions and temperatures. The calculated Gibbs free energies indicate that the homogeneous solid solutions can be stabilized only at temperatures higher than ~ 3000 °C. It was established that lattice vibrations play an important role in reducing the temperature of the stabilization of the solid solutions. The calculated phonon spectra and thermodynamic characteristics indicate that the thermodynamic properties of the alloys will have an extremal behavior depending on composition.