Structure Properties Of Si Clusters Inside Carbon Nanotube

The internal space of carbon nanotubes is limited in nanoscale. The wall of carbon nanotubes is stable. Carbon nanotubes can support and protect the filler inside. And carbon nanotubes can act as a nanoscale mould to make internal filler spiral. In Addition, the filler also can change the original properties of the carbon nanotubes, as well as the compounds consisted of the filler and carbon nanotubes have different properties. In the thesis, with the classical molecular dynamics method and Tersoff potential function, the thermal stability of compound structures of silicon nanowire encapsulated in carbon nanotubes is studied as well as the structure evolution of rapidly solidified Si clusters in the singled-wall carbon nanotubes.The same diameter silicon nanowires with [111] orientation of the cubic diamond structure is filled in some armchair single-walled carbon nanotubes respectively. The heat process of compound structures of silicon nanowire encapsulated in carbon nanotubes are simulated by classical molecular dynamics method. Through the visualization and energy analysis method, the thermal stability of composite structures are studied. The changes of the thermal stability of silicon nanowires and carbon nanotubes are explained by the relationship between carbon nanotubes space constraints and Van der Waals force. It is found that the diameters of the carbon nanotubes make a novel difference to the thermal stability of silicon nanowires inside. When the nanotube diameter is on the small side,thermal stability of silicon nanowires is increased; And when the nanotube diameter increases to a certain size, the thermal stability of silicon nanowires will suddenly drop significantly. Until the distance between silicon nanowires and the wall of carbon nanotube is greater than 1 nm, the thermal stability of silicon nanowires will be restored. On the other hand, silicon nanowires filling into the carbon nanotubes has an effect on decreasing the thermal stability of carbon nanotubes.The rapid solidification process of silicon in(13, 13),(19, 19) and(25, 25) carbon nanotubes with cooling speed of 2×1010 K/s 、1×1011 K/s and 1×1012 K/s are simulated. The structures of silicon clusters are characterized and structures evolution characteristics of silicon clusters are analysis by the visualization, the average coordination number, the bond angle distribution, the dihedral angle distribution method in the process of solidification. It is found that the lower the cool speed the bigger the diameter of carbon nanotube is, the faster the change of the average coordination number of Si. Limited by carbon nanotubes, silicon clusters tend to form the structure contained diamond structure unit in the process of rapid solidification. Furthermore the slower the cooling speed is, the more conducive to form diamond structure units. Besides carbon nanotube diameter size have an effect on forming diamond structure units. With the relatively moderate pipe diameter, the forming ability of diamond structure units is highest in the solidification process of silicon clusters inside carbon nanotubes. With the relatively large pipe diameter or the relatively small pipe diameter, the forming ability of diamond structure units is not highest in the solidification process of silicon clusters inside carbon nanotubes.