First-Principles Study on Electronic and Elastic Properties of Co, Ni, Cu, and Mo-Doped -Si₃N₄

This study employs first-principles calculations to investigate the structural stability, electronic properties, and elastic properties of Co-, Ni-, Cu-, and Mo-doped beta-Si3N4. After optimizing the structure of each doped system, it can be determined that all systems are stable structures, as evidenced by the binding energy and forming energy. Then, the electronic properties of the doped systems are analyzed using the energy band and density of states. The findings reveal that the introduction of Co, Ni, and, Cu, reduces the energy bandgap compared to pure Si3N4. More notably, the doping of Mo eliminates the bandgap and results in strong metallicity in the doped systems. Moreover, all doped systems display magnetic moments. Finally, the investigation of elastic properties shows that all doped structures are ductile. The doping of Co, Ni, Cu, and Mo metals improves the toughness of Si3N4. In addition, the doping change of Co is the most obvious. These findings provide a theoretical foundation for future research on the preparation of ductile Si3N4 ceramics.