The influence of the stacking orientation of C and BN stripes in the structure, energetics, and electronicproperties of BC2N nanotubes

Abstract

Carbon and boron nitride nanotubes present significant differences in theirelectronics. However, they have isoelectronic bonds and very similar geometricalstructures that allow BCN nanotubes to be synthesized. These BCN nanotubespresent properties that can vary according to their relative number of B, C, andN atoms, and their atomic distribution on the nanotube surface. Here weemploy first-principles density functional theory to study BCN nanotubes withBC2N stoichiometry. These nanotubes are composed of pure BN and C stripes which are stacked(i) in parallel, (ii) perpendicularly, and (iii) forming helicoidal patterns along the nanotubeaxes. We found that the different strain energies of the curved C and BN arcs in thenanotubes with parallelly aligned stripes can lead to geometries that deviatesignificantly from the usual circular shape. A sinusoidal shape was predicted for aBC2N nanotube with a helicoidal arrangement of the C and BN stripes due to differences in theC–B and C–N bonds parallel to the tube axis. It was shown that the phase segregation isenergetically favoured. Such structural preference and the relative stability of theBC2N nanotubes can be explained in terms of the ratio between the total number of bonds andthe number of C–B and C–N bonds in the nanotubes. Finally, we found that one type ofBC2N nanotube with helicoidal C and BN stripes, although having a zigzag structure, exhibits ametallic character.