The Characteristic Band Spectrum Of Cagelike Nanostructured Systems

Cagelike nanostructured systems have the feature of small scale, rich surface and interface and present some abnormal properties in virtue of their unique structure. By developing the spV tight-binding model, we study the band spectrum feature of the cagelike structure such as carbon clusters, carbon nanotubes, BN nanotubes in this thesis. The researches of band spectram on the cagelike structures help the unveiling of their properties and application.In chapter 1, the basic characters of cagelike nanostructured systems are briefly introduced, including their preparation, microstructures, properties, and related applications. As an example of carbon clusters, we introduce CM.In chapter 2, we mainly review the bonding and hybridization between s and p orbitals of semiconductor. From the quantum chemistry angle, we introduce the hybridization theories and classification . According to the general views of boinging theories, the hybridization ways of carbon allotropes and BN crystal is discribed. At the end, the tight-binding method and the spV tight-binding model are formulated. Bying constructing the bloch wave function, the Hamiltonian matrix have been formulated and the overlap matrix parameters is fit.The band characteristic spectrum of carbon clusters is reviewed in chapter 3. As an example of carbon allotropes, we describe the band spectrum of graphite and carbonnanotubes. By developing the spV tight-binding model, we calculate band structure and the electronic probability density of C^ molecule. And the calculated energy gap 1.893eV is good agreement with the experimental value 1. 9eV.The band structure and density of state of single-walled BN nanotubes is reviewed in chapter 4. The calculated results show that the band gap of small-radius single-walled BN nanotubes still follows the three ways of CNNTS' although the gap difference is smaller. With the increasing radius, the gap trend to consistent. When the radius is smaller, the band gap is about a stable value 4. 3eV. That is good agreement with the experiment result.In the last chapter, we give a brief summariy and the outlook for the next process in this field is academically given.