Structure and properties of TiN(111)/Si_xN_y/TiN(111) interfaces in superhard nanocomposites: First-principles investigations

摘要

We perform first-principles calculations based on density-functional theory to investigate the role of interfaces in superhard nanocomposites. A prerequisite is clearly knowledge of the detailed atomic structure, which is addressed in the present paper. In particular, we study the relative stability of TiN(111)/Si_xN_y/TiN(111) interfaces, which form in the highly thermally stable nc-TiN/a-Si_xN_y nanocomposites. For nitrogen-rich con-ditions, the most favorable configurations involve very thin layers of Si, which are purely nitrogen coordinated and tetrahedrally bonded. For increasingly nitrogen-poor conditions, interfaces involving Ti-Si-N, and predominantly octahedral Ti-Si-Ti, bonding are preferred. The atomic geometry and associated electronic structure are discussed for these interfaces, as well as properties of the bulk α, β, and γ phases of Si_3N_4, TiN, and TiSi_2.