Interlayer vacancy defects in AA-stacked bilayer graphene: density functional theory predictions.
AA-stacked graphite and closely related structures, where carbon atoms are located in registry in adjacent graphene layers, are a feature of graphitic systems including twisted and folded bilayer graphene, and turbostratic graphite. We present the results of ab initio density functional theory calculations performed to investigate the complexes that are formed from the binding of vacancy defects across neighbouring layers in AA-stacked bilayers. As with AB stacking, the carbon atoms surrounding lattice vacancies can form interlayer structures with sp2bonding that are lower in energy than in-plane reconstructions. The sp2interlayer bonding of adjacent multivacancy defects in registry creates a type of stable sp2bonded 'wormhole' or tunnel defect between the layers. We also identify a new class of 'mezzanine' structure characterised by sp3interlayer bonding, resembling a prismatic vacancy loop. The V6hexavacancy variant, where six sp3carbon atoms sit midway between two carbon layers and bond to both, is substantially more stable than any other vacancy aggregate in AA-stacked layers. Our focus is on vacancy generation and aggregation in the absence of extreme temperatures or intense beams.
Department of Chemistry, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, GU2 7XH, United Kingdom.
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Vuong
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Trevethan
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Latham
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Ewels
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Erbahar
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Briddon
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Rayson
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Heggie