Extensive theoretical studies on small and medium sized boron clusters lead us to the conclusion that boron has a strong potential to form stable nanotubular structures 1 . In addition, recent experimental results by Terrones et al. 2 showed that carbon nanotubes doped with boron atoms tend to concentrate the latter mostly in the form of clusters associated with their tips. Therefore a better understanding of nanotubular boron systems could eventually pay off with respect to the development of future nanotechnologies based on carbon nanotubes.
A careful analysis of the structure and formation of boron clusters shows that boron nanotubes follow precisely the same well-defined set of rules that guides the formation of stable boron compounds. Analogous to carbon, boron nanotubes can be related to stable planar boron compounds by a simple geometrical cut and paste operation. It is particularly interesting to compare the resulting planar and layered forms of boron to well-known layered boron-aluminum compounds.
The most important physical properties that characterize a given material are certainly its mechanical and electronic properties. Under this aspect, we will contrast a number of simple nanotubular boron systems with their carbon and boron-nitrogen based counterparts. A key feature that follows from our numerical simulations is the fact that the strain energy of boron nanotubes turns out to be lower than that of carbon. Also we find that boron nanotubes should be metallic. We hope that these results will stimulate research on boron compounds as a promising basic material for nanotechnology.