The vacancy defects and oxygen atoms occupation effects on mechanical and electronic properties of Mo_(5)Si_(3) silicides

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 Mo_(5)Si_(3).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 Mo_(5)Si_(3) 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 Mo_(5)Si_(3).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 Mo_(5)Si_(3).