To understand the electron doping effect into the parent compound BaFe2As2, we have theoretically evaluated phase stability and electronic structure of low temperature nickel (Ni) doped Ba(Fe1-xNix)2As2 superconductor. The optimized Fmmm phase are calculated by first principles pseudopotential and plane wave calculations within generalized-gradient approximation (GGA) with Perdew-Perke-Ernzerhof (PBE) exchange correlation functional. Our results show that nonmagnetic (NM) and antiferromagnetic (AFM) state having anisotropic spin configuration in the band structure calculation. This finding shows that a clear gap is observed in the band structure upon optimally Ni doping in the NM state with a small indirect gap 43.68 meV is found in the direction of G-X points. A spin gap 47.8 meV is obtained when a spin polarized orbital calculation is introduced to the system. The hybridization of Fe/Ni-3d and As-4p in the density of states (DOS) results a metallic region near the Fermi level and flat bands exist below the level. We suggest the observation provides a crucial understanding in the superconductivity of the materials. � 2016 Author(s).

The electronic structures of "-phase of solid oxygen (O2)4 are studied within the framework of densityfunctional theory. The intriguing molecule has been known to have magnetic properties at room temperature by applying pressure. Nevertheless, until now there was no evidence of band structure studied in the antiferromagnetic behaviour of (O2)4. We report a comparison study for spin and non-spin polarization orbital which suggests that this ferromagnetic configuration of (O2)4 could not be seen experimentally, and antiferromagnetic configuration of (O2)4 was seen at higher pressure of about 10 GPa. The antiferromagnetic state transforms into the superconducting state as the sample temperature decreases. The results can serve as a useful approximation in studying general features of the electronic structure. The (O2)4 clusters are reported in the Raman study, having significant absorption at 1516 cm-1 below infrared region.