The effect of intrinsic point defect on the magnetic properties of ZnO nanowire is investigated by the first-principles calculation based on the density functional theory (DFT). The calculated results reveal that the pure ZnO nanowire without intrinsic point defect is nonmagnetic and ZnO nanowire with VO, Zni, Oi, OZn, or ZnO point defect also is nonmagnetic. However, a strong spin splitting phenomenon is observed in ZnO nanowire with VZn defect sitting on the surface site. The Mulliken population analysis reveals that the oxygen atoms which are close to the VZn defect do major contribution to the magnetic moment. Partial density states calculation further suggests that the appearance of the half-metallic ferromagnetism in ZnO nanorod with VZn originates from the hybridization of the O2p states with Zn 3d states.

In this paper, vertically aligned ZnO nanorod arrays were synthesized by a simple hydrothermal process. The microstructure, morphology and optical properties of the as-prepared samples were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence spectrum (PL). The results show that the vertically aligned ZnO nanorod arrays are hexagonal wurtzite structures with the high (002)-orientation. At room temperature, the PL measurements illustrate that the as-prepared ZnO nanorod arrays exhibit a strong ultraviolet (UV) emission centered at about 378nm and a broad yellow-green emission centered at about 554 nm. A possible origin of the yellow-green emission of the ZnO nanorod arrays related to the intrinsic defect is proposed.

The electronic structure, band structure, density of states (DOS) and electronic density difference of paraelectric SrTiO3 in the cubic phase were performed by the first-principles calculation based on the density functional theory (DFT). The energy levels of high symmetry points in the Brillouin zone were listed and Mulliken population analysis was performed for valence bond structures. The top valence band of SrTiO3 is at the R point, and the minimum of the conduction bands is at the Γ point. The calculated value for indirect band gap is 1.84eV in the Brillouin zone. As in other perovskite ABO3 ferroelectrics, the population analysis, DOS and electron density difference show that there is a very strong hybridization between the Ti3d and O2p states in the valence bands, which is responsible for the ferroelectricity tendency.

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