Investigation Of FeB_N(N=1-10) Clusters By Using Density Functional Theory

The dissertation is devoted to the study of physical and chemical properties of novel clusters from first principles. With the 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. In this dissertation, we study the structures and the electronic properties of FeBN by using density functional theory.In chapter 1, we give a brief introduction to clusters. With a size between those of atoms and macroscopical systems, clusters have many unique properties and attract much experimental and theoretical research attentions. At first, we introduce the basic properties of clusters. Then, some common methods in experimental and theoretical studies on clusters are discussed. In chapter 2, we introduce the basic concept and progress of DFT.Development of quantum chemistry promotes the establishment of DFT. Finding good approximation for exchange-correlation functional is one of the main targets in DFT and we discuss it in detail. At end of this chapter, we briefly introduce the simulation package used in the work.At the last chapter, we study the the structures and the electronic properties by using DFT with PW91 exchange-correlation functional. Some interesting results are discussed here. These results indicate that the ground states of FeBN clusters often absorb 3D structures and FeB4 and FeB8 is more stable than any other cluster. Also, we studied magnetism properties of the ground-state clusters systematically and found that the magnetic moment of Fe atom and total magnetic moment are oscillation with the increasing of cluster size.