Stability investigation and thermal behavior of a hypothetical silicon nanotube

Abstract

Even though silicon nanotubes have never been observed, this paper attempts to establish the theoretical similarities and differences between Si and C structures. Through the use of two alternative theoretical approaches, the first principles calculations and empirical potential, the electronic and structural properties of this hypothetical material are examined. The first principles calculations are based on the density-functional theory and it is shown that depending on their chiralities and diameters, the silicon nanotubes may present metallic (armchair) or semiconductor (zigzag and mixed) behaviors, similar to carbon structures. It is shown that the gap decreases in inverse proportion to the diameter, thus approaching zero for planar graphite, as was expected. In the second alternative approach, the Monte Carlo simulations are used with the Tersoff's empirical potential to present a systematic study on the thermal behavior of these new structures. It is shown that similarities like band structures and density of states are observed between the C and Si nanotubes. Nevertheless, there are relevant discrepancies in the thermal stabilities and energy differences between the cohesive energies per atom for the two tubes, compared with the corresponding bulks, implying the very improbable structure of the silicon nanotubes.