B3LYP Hybrid Density Functional Study On Some New Materials

Along with the rapid development of computational methods and computer technology, computational chemistry has become more and more important in modern chemistry. Due to its moderate computational consume and high precision, density functional theory (DFT) has become one of the most important methods in computational chemistry. The hybrid density functional B3LYP has been widely applied to calculate molecules and clusters. The great success has been acknowledged especially by chemists. In this dissertation, the B3LYP functional is extended to calculate some other complicated systems such as solid and surface. We study a variety of materials with different dimensions, from simple cluster, nanotube, to solid and surface. The concerned properties include geometry, electronic structure, magnetic order and piezoelectric properties.In Chapter 1, we introduce the basic concept and progress of DFT. Development of quantum chemistry promotes the establishment of DFT. Thomas-Fermi model is the first theory using density of electrons as the main variable. Theorem of Hohenberg-Kohn is the fundament of DFT and is developed to Kohn-Sham equation, which can be used to perform real calculations. Now, new corrections and extensions, together with developed exchange-correlation functionals, especially the hybrid density functional, have made DFT more accurate and suitable for more systems. We also introduce the basic concept and progress of time-dependent DFT. At the end of this chapter, we introduce some widely used simulation packages.In Chapter 2, we study two kinds of clusters —V₂O₆ and WO₄. With a size between those of atoms and macroscopical systems, clusters have many...