Effect of Vacancy Defects on the Properties of CoS₂ and FeS₂

In order to explore the effect of vacancy defects on the structural, electronic, magnetic and optical properties of CoS₂ and FeS₂, first-principles calculation method was used to investigate the alloys. The calculated results of materials without vacancy are consistent with those reported in the literatures, while the results of materials with vacancy defect were different from those of literatures due to the difference vacancy concentration. The Co vacancy defect hardly changes the half-metallic characteristic of CoS₂. The Fe vacancy defect changes FeS₂ from semiconductor to half-metal, and the bottom of the spin-down conduction band changes from the p orbital state of S to the d(t_2g) orbital state of Fe, while the top of the valence band remains the d orbital d(e_g) state of Fe. The half-metallic Co vacancy defects of CoS₂ and Fe vacancy defects of FeS₂ are expected to be used in spintronic devices. S vacancy defects make both CoS₂ and FeS₂ metallic. Both the Co and S vacancy defects lead to the decrease of the magnetic moment of CoS₂, while both the Fe and S vacancy defects lead to the obvious magnetic property of FeS₂. Vacancy defects enhance the absorption coefficient of infrared band and long band of visible light obviously, and produce obvious red shift phenomenon, which is expected to be used in photoelectric devices.