The Study Of Structural And Electronic Properties Of Eu_n（B₄N₄H₈）_n+1（n=1-4）sandwish Clusters And The Nanowires

Low-dimensional nanomaterials have particular structures, which make them have unique properties from corresponding bulk materials. The discovery of ferrocene(Fe Cp2, Cp=C5H5) opens a new field for the study of low-dimensional nanomaterials. The sandwich clusters and the one-dimension nanowires consist of metal atoms and annular molecules have peculiar physical and chemical properties. They have huge potential applications in many aspects, such as national defense science, industrial catalysis, biological medicine, high-performance photoelectric device and so on. Therefore, these materials have been widely studied so far. In recent years, researchers have obtained fruitful results based on theoretical or experimental studies. In this paper, by using density functional theory and VASP package, we theoretically investigated the structures and electronic properties of inorganic sandwich clusters Eun(B4N4H8)n+1(n=1-4) and the corresponding nanowires. The main contents are as follows.In the first chapter, we mainly introduced the theoretical background and the practical applications of low-dimensional nanomaterials. Specially, wediscussed the recent studies on small sandwich clusters and the one-dimensional sandwich nanowires. At the end of the chapter, we suggested the purpose and significance of present study. The second chapter presented the theoretical background of present study, including the information about first-principle calculation, density functional theory, and VASP package used here.In the third chapter, we calculated the structures and electronic properties of the inorganic sandwich clusters Eun(B4N4H8)n+1(n=1-4). We considered many different initial structures. By optimizing these structures, we found that the ground-state structures with n<4 are similar, i.e., all the ligand molecule overlap completely along the molecule axis. While the ground-state structure of Eu4(B4N4H8)5 has been changed compared to the smaller ones, i.e., the middle ligand molecule is rotated by 45°. We also found if the ligand rings are rotated, it will have significant influences on the structures, indicating these molecules are not free. In addition, the binding energies of the clusters are very large, thus they are stable. Our results show that the ground states of all the clusters are anti-ferromagnetic, and the energy gap varies with the cluster size. The total magnetic moment of cluster is mainly provided by Eu and the magnetic properties of Eun(B4N4H8)n+1 are different from its organic counterparts Eun(COT)n+1. For Eun(COT)n+1 clusters, the total magnetic moments increase linearly with the cluster size.In the fourth chapter, we extended the study from the finite clusters to the one-dimensional infinite sandwich nanowire [Eu(B4N4H8)]∞ and investigated thestructures and electronic properties. We selected three initial structures for[Eu(B4N4H8)]∞ and found these structures are all stable. The ground state of the nanowire is ferromagnetic. In addition, the electronic band and the density of states show that the three structures are semiconductors with small gaps. The energy between the ferromagnetic and anti-ferromagnetic states are small,indicating that [Eu(B4N4H8)]∞ may have many different spin states.The conclusions are summarized in the fifth chapter.