Sublattice segregation of hydrogen adsorbates in carbon nanotubes

Recent experimental observations have reported that, rather than randomly distributed, nitrogen atoms may prefer to be located on one of the two sublattices of graphene. It has been suggested that such a preference may present a possible avenue to tailor the band gap of graphene while maintaining its excellent electronic transport properties. Among the proposed mechanisms to explain this effect is the suggestion that long-range interimpurity interactions mediated by the conduction electrons of graphene may give rise to the asymmetry between sublattice occupations. Electron-mediated interactions are known to be prevalent not only between N atoms but also between impurities that are adsorbed to a specific location within the hexagonal structure, namely to the top of the carbon atom. Furthermore, this interaction is known to become more long ranged as the dimensionality of the system is lowered. For that reason, in this paper we investigate whether a similar sublattice asymmetry appears in the case of metallic carbon nanotubes doped with hydrogen adatoms. Our results indicate that similar sublattice asymmetries are observable and even more pronounced in small-diameter CNTs with a dilute concentration of adsorbates, diminishing with increasing diameter or impurity concentrations.