Influence of point defects on charge transport in nickel ferrite NiFe2O4

• Published in: Computational materials science Vol. 246
• Main Authors: Fominykh, Nikita A., Situmeang, Jesaya, Stegailov, Vladimir V., Kaun, Chao-Cheng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-01-2025
• Subjects: Conductivity; DFT+U; Electronic structure; NEGF-DFT; Polaron hopping; Conductivity; Electronic structure; NEGF-DFT; DFT+U; Polaron hopping
• ISSN: 0927-0256
• DOI: 10.1016/j.commatsci.2024.113326

The paper considers electronic structure of pristine and defective nickel ferrite (spinel NiFe2O4). The orbital ordering, band gap and charge transfer are studied in the framework of density functional theory with account of strong electronic correlations (DFT+U method). The possibility of changing the type of polaron transport in the presence of oxygen vacancies and nickel antisites has been demonstrated. The corresponding non-adiabatic activation barriers of polaron transport is considered. The resulting hopping energies are in general agreement with experimentally observed activation energies. The highlighted influence of point defects on the polaron conductivity mechanism could be a suitable explanation for the large variability of activation energies in previous experimental works. NEGF-DFT calculations were also performed to consider a possible band conduction mechanism. The enhanced conduction with the presence of oxygen bi-vacancies, and a change in carrier type is also observed.
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•Two conduction mechanisms in NiFe 2 O 4 have been investigated in the DFT+U framework.•We show that point defects can change the carrier type of polaron hopping.•NEGF-DFT calculations suggest that oxygen vacancy filaments offer conduction channels.