True nanocable assemblies with insulating BN nanotube sheaths and conducting Cu nanowire cores

Nanocable models comprised of BN nanotubes filled with close-packed Cu nanowires were investigated by gradient-corrected density functional theory (DFT) computations. The optimal distance between the sidewall of BN nanotubes and the atoms in a copper nanowire is about 0.35 nm, with a weak insertion energy (ca. -0.04 eV per Cu atom). Hence, such nanocables are assembled by weaker van der Waals (vdW) forces, rather than by chemical bonding interactions. The electronic band structures of the BN/Cu hybrid systems are superposition of those of the separate components, the BN nanotubes, and the Cu nanowires. Since charge density analyses show that the conduction electrons are distributed only on the copper atoms, charge transport will occur only in these inner nanowires, which are effectively insulated by the outer BN nanotubes. On the basis of these computational results, BN/Cu hybrid structures should be ideal nanocables.