Improving brittle behavior and mechanical properties is still a big challenge for high-temperature structural materials. By means of first-principles calculations, in this paper, we systematically investigate the effect of vacancy and oxygen occupation on the elastic properties and brittle-or-ductile behavior on Mo₅Si₃. Four vacancies (Si_–Va1, Si_–Va2, Mo_–Va1, Mo_–Va2) and oxygen occupation models (O_–Mo1, O_–Mo2, O_–Si1, O_–Si2) are selected for research. It is found that Mo_–Va2 vacancy has the stronger structural stability in the ground state in comparison with other vacancies. Besides, the deformation resistance and hardness of the parent Mo₅Si₃ are weakened due to the introduction of different vacancy defects and oxygen occupation. The ratio of B/G indicates that oxygen atoms occupation and vacancy defects result in brittle-to-ductile transition for Mo₅Si₃. These vacancies and the oxygen atoms occupation change the localized hybridization between Mo–Si and Mo–Mo atoms. The weaker O–Mo bond is a contributing factor for the excellent ductile behavior in the O_-Si2 model for Mo₅Si₃.

改善脆性行为和机械性能仍然是高温结构材料的一大挑战。通过第一性原理计算，本文系统地研究了空位和氧占据对Mo ₅ Si ₃的弹性性能和脆性或延性行为的影响。选择四个空位（Si _–Va1、Si _–Va2、Mo _–Va1、Mo _–Va2）和氧占据模型（O _–Mo1、O _–Mo2、O _–Si1、O _–Si2）进行研究。发现 Mo- _Va2与其他空位相比，空位在基态下具有更强的结构稳定性。此外，由于引入不同的空位缺陷和氧占据，母体Mo ₅ Si ₃的变形抗力和硬度减弱。B / G的比值表明氧原子占据和空位缺陷导致Mo ₅ Si _{3 的}脆-韧转变。这些空位和氧原子占据改变了 Mo-Si 和 Mo-Mo 原子之间的局部杂化。较弱的 O-Mo 键是Mo ₅ Si ₃的 O _-Si2模型中优异的延展性的一个促成因素.