Single-wall carbon nanotubes (SWCNTs) have unusual physico-chemical properties and find widest use in the synthesis of novel composite materials for micro and nanoelectronics, micro and nanofluidics, micro and nanopower devices, and biomedical applications. However, these properties are strongly dependent on the helicity degree or so-called chirality. Thus, designing a selective synthesis process capable of producing SWCNTs of specific chiralities is crucial to take full advantage of these properties.

Typical SWCNTs syntheses use a carbon-containing source and a suitable catalyst that facilitates the formation of stable nanotube structures. During synthesis nanotube emerges upon nucleation of carbon atoms on a metal nanocatalyst surface, and it grows by subsequent addition of carbon species to the nanotube rim.

But it is not known how certain nanotube chiralities might be favored over others during synthesis. Therefore, uncovering the reasons that bias the formation of near-armchair instead of near-zig-zag chiralities is a first step in the ultimate goal of obtaining specific chiral SWCNTs by design.

A natural way to improve the understanding of the synthesis and properties of nanostructures is the use of ab initio computational tools. In a systematic theoretical study recently published in Nanotechnology, these tools are applied to investigate

The possible mechanisms suggests that the growth kinetics of near-armchair SWCNTs is more favorable than that of near-zig-zag tubes, since successive additions of C2 radicals to the geometric/electronic conformation of nascent near-armchair structures lead to an increase of the number of active sites in the nanotube rim as the reaction progresses. Favorable near-armchair growth is also suggested by frontier orbitals reactivity and tendency of tube realignment controlling mechanical growth stoppage.