Stability investigation and thermal behavior of a hypothetical silicon nanotube

dEven though silicon nanotubes have never been observed, this paper attempt s to establish the theoretical similarities and differences between Si and C structures. Through the use of two alternative theoretical approaches, th e first principles calculations and empirical potential, the electronic and structural properties of this hypothetical material are examined. The firs t principles calculations are based on the density-functional theory and it is shown that depending on their chiralities and diameters, the silicon na notubes may present metallic (armchair) or semiconductor (zigzag and mixed) behaviors, similar to carbon structures. It is shown that the gap decrease s in inverse proportion to the diameter, thus approaching zero for planar g raphite, as was expected. In the second alternative approach, the Monte Car lo simulations are used with the Tersoff's empirical potential to present a systematic study on the thermal behavior of these new structures, It is sh own that similarities like band structures and density of states are observ ed between the C and Si nanotubes. Nevertheless, there are relevant discrep ancies in the thermal stabilities and energy differences between the cohesi ve energies per atom for the two tubes, compared with the corresponding bul ks, implying the very improbable structure of the silicon nanotubes. (C) 20 01 Elsevier Science B.V. All rights reserved.