First-principles calculations of substitutional defects and vacancies are performed for zigzag-edged hybrid C/BN nanosheets and nanotubes which recently have been proposed to exhibit half-metallic properties. The formation energies show that defects form preferentially at the interfaces between graphene and BN domains rather than in the middle of these domains, and that substitutional defects dominate over vacancies. Chemical control can be used to favor localization of defects at C- B interfaces (nitrogen-rich environment) or C-N interfaces (nitrogen-poor environment). Although large defect concentrations have been considered here (106 cm-1), half-metallic properties can subsist when defects are localized at the C-B interface and for negatively charged defects localized at the C- N interface, hence the promising magnetic properties theoretically predicted for these zigzag-edged nanointerfaces might not be destroyed by point defects if these are conveniently engineered during synthesis.
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