Carbon nanotube superarchitectures: An ab initio study

An advantage of using single-walled carbon nanotubes (SWCNTs) as building blocks in tailoring materials functionality is that many unique properties of SWCNTs can be captured. We present an ab initio study of covalent assembly of SWCNTs into a variety of functional carbon superarchitectures, including two-dimensional (2D) hexagonal and orthogonal and 3D simple cubic (or orthogonal), stacked hexagonal, diamond-like superarchitectures. To achieve a sensible design of SWCNT-based functional materials, we have explored the nodal structures and connectivity, particularly, relative stability of various topological defect-containing junctions at the nodal (or joint) region. The quantum-chemical calculations suggest that the 2D hexagonal SWCNT superarchitectures are universally semiconducting, while 3D SWCNT superarchitectures are mostly metallic, regardless of whether the constituent SWCNTs are metallic or semiconducting. In particular, for the metallic SWCNT superarchitectures, their electronic properties are insensitive to the electronic properties of constituent SWCNTs. This remarkable property of SWCNT superarchitectures may be exploited to dodge the experimental subtlety for separation of metallic from semiconducting SWCNTs in CNT bundles. We have also calculated elastic constants of the SWCNT superarchitectures. We predict that SWCNT superarchitectures can be mechanically as robust as many solid semiconductors and metals. In view of their high specific surface area for materials functionality, the metallic SWCNT superarchitectures may find applications in fuel cells, battery electrodes, or nanoelectronic devices.