Theoretical Studies Of Nano-Materials And Development Of Linear Scaling Electronic Structure Methods

With the rapid progress in density functional theory (DFT) and its numerical methods, DFT based first-principles calculation has become a routine method for condensed matter theory, quantum chemistry and material science. Due to the peculiar properties, such as optical, electronic, magnetic, thermal, mechanic properties of nanostructures, nanomaterials have attracted much research interest. Although nano-technology is still on elementary stage, nano-technology based on nano-materials will play an important role in modern economy and development in the 21th Century. Theoretical studies are indispensable for understanding the properties of nano-materials and designing novel nano-materials. On the other hand, since traditional first principles methods are computational demanding, thus it is necessary to develop fast especially linear scaling methods.There are two parts in the dissertation: The first part incuding chapter 1 to chapter 5 focuses on the theoretical studies on various nano-materials. Other materials for instance boron doped diamond superconductor is also considered. In the second part (chapter 6 and chapter 7), we have developed some linear scaling methods to deal with large scale systems.In the first chapter, we introduce the basic concept of DFT and review its recent progress. In electron density based DFT, all ground state properties can be derived from the electron density. Finding good approximation for exchange-correlation functional is one of the main targets in DFT. In the last, we introduce briefly the density functional packages used in the current work.In chapter 2, we focus on boron nitride nanotubes and fluorinated boron nitride nanotubes. The structural, electronic, and vibrational properties of small-radius single-walled BN nanotubes are studied using the density functional method with the local density approximation. The results show that...