Abstract
Systematic density functional theory calculations were carried out to study the structural, electronic, magnetic and optical properties of vacancy and antisite defects in marcasite FeS2 (m-FeS2). Five types of point defects were considered, that is S vacancy, Fe vacancy, FeS divacancy, Fe substitute S site and S substitute Fe site. The results show that Fe substitute S, S vacancy and Fe vacancy are the dominant defects in m-FeS2. The defects remarkably affect the electrical, optical performances of the m-FeS2, and even induce magnetism. All the considered point defects have defect states in the band gap of perfect m-FeS2. We estimated the stability of magnetic state and found that the m-FeS2 with point defects shows magnetic ground state except S vacancy case. Detailed analysis shows that m-FeS2 with S vacancy is a nonmagnetic semiconductor, with Fe vacancy, FeS divacancy and Fe substitute S site become magnetic metal while with S substitute Fe site is a magnetic semiconductor. In addition, compared with perfect m-FeS2, the static dielectric constants and static refractive indexes of m-FeS2 with defects are all increased significantly, the absorption coefficients show red shifts and enhancements in the infrared region due to the defect states.
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