Structure and properties of TiN„111... /SixNy/TiN„111... interfaces in superhard nanocomposites: First-principles investigations

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 /SixNy/TiN 111 interfaces, which form in the highly thermally stable nc-TiN/a-SixNy nanocomposites. For nitrogen-rich conditions, 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 , , and phases of Si3N4, TiN, and TiSi2.