Vacancy and Oxygen Substitution for Nitrogen-Induced Structural Stability of Ta2N3

First-principles calculations were carried out to investigate the structural stability of synthesized orthorhombic Ta2N3. It is found that the stoichiometric orthorhombic Ta2N3 is unstable below 20 GPa. However, it can be stabilized by a small amount of nitrogen vacancies or oxygen substitution into nitrogen sites. The calculated electron localization function indicates that both the formation of nitrogen vacancy and the substitution of oxygen atom can enhance the Ta-N bonding, which is essential for the structural stability. Furthermore, both oxygen substitution and nitrogen vacancy plays a similar role in stabilizing the orthorhombic lattice of Ta2N3. The results of our calculations show that nitrogen vacancies or oxygen substitution into nitrogen sites can alter the charge distribution over the unit cell, which leads to a new arrangement of atoms and enhanced Ta-N bonds.