The effects of vacancies defects and oxygen atoms occupation on physical properties of chromium silicide from a first-principles calculations

In present work, the effects of vacancy defects on the mechanical and thermodynamic properties of Cr5Si3 have been investigated using the first-principles. The occupation mechanism of oxygen atoms in Cr5Si3 is also carefully analyzed and discussed. The vacancy formation, lattice vibrations, electronic structure, elasticity and thermodynamic parameters of Cr5Si3 were calculated separately. The results show that Cr5Si3 is stable and irrespective of the presence of vacancies or oxygen atoms occupation in it. In addition, the Si vacancies cause Cr5Si3 to undergo a brittle to ductile transition, which originates the weak hybridization between Cr and Si atoms. Importantly, when the Si-Va2 vacancy is occupied by oxygen atom, Cr5Si3 undergoes a brittle to ductile transition despite its poor hardness and resistance to deformation, which is attributed to the formation of weak Cr-O bonds. Furthermore, both the presence of vacancy defects and the introduction of oxygen atoms result in Cr5Si3 exhibiting the greater phase stability and better thermal properties.