First-principles studies of the electronic properties of native and substitutional anionic defects in bulk iron pyrite

Systematic spin-polarized density functional theory calculations were performed to investigate the formation energies of native and substitutional anionic point defects in iron pyrite (FeS2) and their impact on bulk electronic structure. A detailed analysis indicates that neutral sulfur and iron vacancies do not act as efficient donors or acceptors. We find that substitutional oxygen does not induce gap states in pyrite and can actually passivate gap states created by sulfur vacancies. Most Group V and VII impurities create mid-gap states and produce spin polarization. In particular, Cl and Br are shallow donors that introduce delocalized spin-polarized electrons for potential use in photovoltaic and spintronics applications.