Hexagonal silicon nanotube confined inside a carbon nanotube: A first-principles study

We studied the stability, geometrical structures and electronic energy band of hexagonal silicon nanotube (SiNT) confined inside carbon nanotubes based on first-principle calculations. The results show that the encapsulating process of SiNT is exothermic in (9, 9) carbon nanotube while endothermic in (8, 8) and (7, 7) carbon nanotubes. When the SiNT is inserted into (9, 9) carbon nanotube, the insertion energy is about 0.09 ev. Energy band of SiNT@(9, 9) nanotube is not distorted greatly compared with the superposition of bands of isolated SiNT and (9, 9) carbon nanotube. Especially, a parabolic band occurs near the Fermi level of energy band in SiNT@(7, 7) nanotube. Such a band could be a nearly free electronic state originating from carbon nanotube. Moreover, we discuss the variation of total energy as the SiNT rotates around its axis inside carbon nanotubes. (C) 2007 Elsevier B.V. All rights reserved.