  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.
