First-Principles Study on the Structural and Electronic Properties of Pure and Cobalt-doped α-NiS

Abstract

The crystal structure, average bond length, electronic charge distribution, band structure, and density of states (DOS) of pure and cobalt (Co) doped α-NiS were studied using first-principles calculation based on density functional theory with the addition of Hubbard U (DFT+U) with Local Density Approximation with Ceperly Adler Perdew and Zunger (LDA-CAPZ). One of the purposes of selecting cobalt as a doping atom is its highly effective charge on the Co atom, which can boost the electrical conductivity and enhance the performance of energy storage devices. This work required the convergence test, and k-point values were conducted to ensure the accuracy of the calculations. The lattice parameters of pure α-NiS crystal structure are in the hexagonal space group (P63/mmc), which displays a good agreement compared with the previous experimental work. The average bond length for pure NiS increases with the supercell Co-doped α-NiS crystal structure. For electronic properties, the energy band gap of pure and Co-doped α-NiS shows a good result which contributes higher than the experimental band gap. These results have been done with the recognition of Hubbard U value after the supercell crystal structure displays a lower energy band gap. The electronic charge distribution of pure and Co doped α-NiS are also illustrated to identify whether the bonding characteristics are ionic or covalent bonds. The density of states represents the hybridization state of Co 3d, Ni 3d, and S 3p orbitals at the conduction band (CB) and valence band (VB). The bonding populations refer to the bonding characteristics of pure and Co-doped α-NiS.