Crystalline-to-amorphous transition in Ti1-x Six N solid solution and the stability of fcc SiN studied by combined ab initio density functional theory and thermodynamic calculations

Gibbs free energies of the quasibinary Ti Ny -Si Ny system are constructed to study the relative phase stability of the metastable ternary fcc(NaCl type) and amorphous Ti1-x Six Ny solution phases over the entire range of compositions. The predicted cross point at about x=0.20-0.24 is supported by the published results from physical vapor deposition and chemical vapor deposition experiments. Based on the calculated properties of fcc-SiN phase, the physical origin of the formation of the amorphous phase is addressed.