DFT Study of the Cation Distribution on Stability, Structural and Electronic Properties of Ni-Doped Spinel Co3O4

Abstract

The origin of spinel cobaltite properties can be attributed to the cation distribution between tetrahedral and octahedral coordination. The choice of spinel types is primarily considered due to the different octahedral and tetrahedral crystal fields where the degeneration of the 3d orbital is different and could lead to dissimilar electronic properties. In this work, a theoretical study based density functional theory (DFT) by using CASTEP was performed on Ni-doped Co₃O₄ (NiCo₂O₄) to explore the structural, magnetic and electronic properties. From the computed inversion energy and formation energy study, the resulting NiCo₂O₄ is energetically favorable in inverse spinel type where Ni prefers to substitute with Co at the octahedral site. The result revealed that the substitution of Ni cation has substantially changed the structure from cubic to tetragonal due to the elongation of the Ni-O bonding at the octahedral site which caused Jahn-Teller (JT) distortion. DOS results showed that NiCo₂O₄ has transformed from semiconductor Co₃O₄ into half-metallic material as seen in the spin-down channel which crossed the Fermi level. In addition, details of octahedral crystal field splitting have demonstrated the reason for Jahn-Teller distortion in NiCo₂O₄.