Hybrid density functional theory description of N- and C-doping of NiO

Abstract

The large intrinsic bandgap of NiO hinders its potential application as a photocatalyst under visible-light irradiation. In this study, we have performed first-principles screened exchange hybrid density functional theory with the HSE06 functional calculations of N- and C-doped NiO to investigate the effect of doping on the electronic structure of NiO. C-doping at an oxygen site induces gap states due to the dopant, the positions of which suggest that the top of the valence band is made up primarily of C 2p-derived states with some Ni 3d contributions, and the lowest-energy empty state is in the middle of the gap. This leads to an effective bandgap of 1.7 eV, which is of potential interest for photocatalytic applications. N-doping induces comparatively little dopant-Ni 3d interactions, but results in similar positions of dopant-induced states, i.e., the top of the valence band is made up of dopant 2p states and the lowest unoccupied state is the empty gap state derived from the dopant, leading to bandgap narrowing. With the hybrid density functional theory (DFT) results available, we discuss issues with the DFT corrected for on-site Coulomb description of these systems

Band gap engineering of (N, Si)-codoped TiO2from hybrid density functional theory calculations

“…The exact exchange contribution of 25% was used and this produced a band gap of 3.20 eV for anatase-TiO 2 , in essentially exact quantitative agreement with the experimental value [21], and far superior to previous conventional DFT modelling of titania by both ourselves [7,8] and others [2,6,9,11,12]; this exact exchange contribution of 25% was also suggested originally by Becke by fits of atomization energy data of molecules and is reasonably applicable to a wide extent of materials in hybrid-DFT [22]. It should be noted that the use of the hybrid HSE06 functional has led to improved results in recent studies of the electronic properties of a wide variety of materials vis-à-vis previous nonhybrid DFT and DFT + U studies, such as the technologically important SiC [23], NiO [24] and, importantly for this study, titania [10,14,[25][26][27]; therefore, this serves as a useful motivation for the use of HSE06 in this study. In addition, Deák et al [28] concluded that the HSE06 functional offers improved accuracy for the energetics of defect levels and associated charge transition levels in a variety of materials, as well as describing group-IV semiconductors well.…”

Insights into Syngas Combustion on a Defective NiO Surface for Chemical Looping Combustion: Oxygen Migration and Vacancy Effects

“…The calculations are conducted using the generalized gradient approximation (GGA) of the Perdew–Burke–Ernzerh (PBE) exchange-correlation functional, which is modified by the unrestricted Hubbard- U correction for the strong on-site Coulomb interaction. , The modifiers (i.e., U and J ) applied on Ni are U = 6.3 eV and J = 1.0 eV . On the basis of the experimental outcomes, the chosen terms for the Hubbard- U correction have captured the behavior of the studied system. − Moreover, the computational prediction of the lattice constants of NiO ( a = b = c = 4.161 Å and α = β = γ = 90°) obtained from this study is consistent with experimental observations ( a = b = c = 4.15 Å and α = β = γ = 90°) . The projector-augmented wave (PAW) , method is chosen to treat the core–valence electron interactions.…”

Trends in non-metal doping of the SrTiO3 surface: a hybrid density functional study

“…[20][21][22][23] Generally, replacing O atoms with other non-metal elements will influence the electronic structures of semiconductors. [49][50][51][52] As shown in Fig. 4(a) and (b), C-doping introduces three band gap states of C 2p orbital character in the spin-up and spindown bands.…”