GGA+U and hybrid functional calculations of intrinsic defects and transition metal doping in NiO

Nickel oxide (NiO) is a transparent conducting oxide which has become an active area of research due to it's potential to be used in the next generation of Resistive RAM (RRAM) and Solar Cell devices. Thus it is of interest to study the intrinsic defects responsible for this resistive switching mechanism as well as transition metal (TM) dopants (Fe, Cu, Ag,) in order to improve desired characteristics. Density Functional Theory (DFT) together with the VASP-PAW method based ab initio calculations was used to study the effects of introducing these into rocksalt NiO. Exchange-correlation effects were included in the calculations within the generalized gradient approximation where to better describe the d-orbitals of Ni and TM-dopants a Hubbard potential U contribution was added (GGA+U). Results also considering a hybrid functional (HSE06) to treat the exchange correlation are shown for both the pristine and TM-doped systems. Doped NiO systems were studied using supercells grown along the [111] direction of 32 to simulate anti-ferromagnetic configurations. Stability of these systems was investigated through the calculation of formation energies of these systems in order to discern what is most energetically favorable.