| Alkaline-earth metal oxides have attracted increasing interest due to their potential applications in many technological applications. Those applications require a complete understanding of the electronic properties and optical absorption spectrum of this material. Density functional theory(DFT)(LDA and GGA) although accurately calculate the electronic band structure, energy gap and electronic space distribution on the metal materials. When calculating the ground state properties of insulators and semiconductors, their energy gaps are apparently smaller than the reliable experimental results. We need many-body perturbation theory to correct the energy gaps of insulators and semiconductors underestimated by using density functional theory. Many-body perturbation theory is a first-principles method based on density functional theory(calculation result of DFT used as the zero order approximation) and based on the Greenfunction equations. In this thesis, we use the following approaches of the many-body perturbation theory: 1) The ground state of the material is determined by DFT-LDA methods; 2) The electronic band structure is evaluated using GW methods; 3) The electron-hole excitations are described within Bethe-Salpeter equation including the electron-hole interaction; 4) With results of electronhole excited states, the optical absorption spectrum of the material is calculated.This master thesis is divided into three chapters in total. The first chapter briefly summarizes the density functional theory and the primary principle of many-body perturbation theory. The second chapter presents the calculation results of many-body perturbation theory during my master’s studies for the electronic band structures and electron- hole excited states of bulk CaO, SrO, and BaO and HCl: MgO(001) surface. The calculation results conform well with the experimental results. The future further studies after this work are given in the last chapter. |
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