Nitrogen doping concentration influence on NaNbO3 from first-principle calculations

• This study investigated the crystal structures and electronic structures of NaNbO3−xNx with various nitrogen concentrations based on first principles calculation.
• Under light nitrogen doping (≤4.17 at%), N isolated states formed above the top of valence band (O 2p).
• Under higher doping (≥8.33 at%), the N 2p states mixed with O 2p states so as to narrow the band gap.
• These findings provide a reasonable explanation to recent available experimental results.

The nitrogen concentration effects on electronic band structures and photocatalytic performance of N-doped sodium niobate (NaNbO3) have been investigated by first-principles calculations based on density functional theory (DFT). At lower nitrogen doping levels, some localized N 2p states are formed above the valence band (O 2p) in N-doped NaNbO3, leading to the reduction of the photon transition energy in comparison to that of undoped compound. Under higher doping levels, the N 2p states mix with O 2p states and then move the top of valence band upward. Two possible mechanisms for increasing visible light absorbance in N-doped NaNbO3 are tentatively put forward according to the doping levels, which would be of importance in understanding and developing the visible-light-sensitive nitrogen-doped multimetal oxide.

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