Theoretical Study Of The Structure Evolution Process And The Electronic Properties Of Armchair Single Andmulti-walled Silicon Nanotubes Based On Density Functional Theory

In this paper, the density functional theory(DFT) for single, multi walled tubular silicon clusters and single and multi walled silicon nanotubes geometric structure, electronic properties, stability and from the single and multi walled silicon clusters to the structure of single and multi walled armchair silicon nanotubes study the evolution process. The paper mainly includes the following. The first chapter in this part introduces nano materials, clusters and nanotube structure, properties, preparation methods and growth mechanism, indicating that the single, multi walled tubular silicon clusters and single and multi walled silicon nanotube research meaning and value.In the second chapter, we introduce the density functional theory, and introduce the Gaussian computing software and the basis set for this research.In the third chapter, the evolution process, stability and electronic properties of single and multi walled silicon tubular clusters are studied. In the evolution process to the shorter single, multi walled tubular silicone clusters of geometric structures and electronic properties of were studied. And then, the by layer growth method to get longer single and multi walled tubular silicon clusters, and conducts the research. The results show that single, multi walled tubular silicone clusters of geometric structure and electronic properties gradually approaching the infinite single and multi walled silicon nanotubes with increasing length. In order to stabilize the silicon tubular optimization without imaginary frequency clusters as the foundation, construction and research of infinite single and multi wall silicon nanotubes using periodic boundary conditions. The geometric parameters of the local configuration on the evolution process of the tracking measurement found that with the increase in the length of the tubular Silicon C lusters Growth from the global reconstruction into local reconstruction, and finally evolved into the infinite silicon nanotubes. The electronic properties of frontier molecular orbitals and binding energies respectively reflect the growth trend of silicon nanotubes and the growth process is becoming more and more stable. The density of States and band research shows that all the silicon nanotubes with smaller quasi direct band gap; armchair silicon nanotubes is a wide band gap semiconductor category. With the increase of diameter, the band gap increased slightly. But as the number of tube wall decreases. Silicon nanotubes have a macro conductive quasi direct band gap semiconductor.The fourth chapter is the summary and Prospect of this paper. This paper summarizes the research results, to provide theoretical guidance for the exploration of growth mechanism of silicon nanotubes, and the subsequent sustainable work of this study is prospected.