First-principles Study Of The Structure And Optical Properties Of The High-pressure Alkali Metal (li, Na, K)

High Pressure Physics is an academic discipline which studies the physical behavior of materials under high pressure physical conditions. It has aroused worldwide attention. Under high pressure, materials will show certain properties, which are different from its performance under normal conditions, even making the metal materials to insulator or semiconductor. It's very important for synthesizing new materials. However, in recent years, the first-principles method based on the density functional theory has become the main calculating and study method for material sciences.In view of the complex changing behavior of the electronic structures and optical properties of the alkali metals in loading conditions, the structures and optical properties of three alkali metals (Li,Na,K) were investigated by using the first-principles method under high pressure in this thesis. First, the electronic structures and optical properties of three alkali metals (Li,Na,K) were studied by the first-principles method. And then the optical properties of Li,Na,K under Hydrostatic Pressure were also investigated by calculating and analyzing in details their absorption spectra, refractive index, reflectivity. And it points out that the impact which Hydrostatic Pressure takes on the optical properties. Finally, the changes of optical properties of three alkali metals (Li,Na,K) were studied by pressurizing a Single Axis. Furthermore, by means of studying the changing behavior of metal materials caused by outer electrons from micro perspectives, this thesis elaborates the essential origins of the changes of optical properties. The results show that optical properties of alkali metals (Li,Na,K) change. It provides an important experimental and theoretical basis for the development of alkali metal.