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The Electronic Structure and Optical Properties of Diamond and Zirconia under Shock Compression

Author: YinJun
Tutor: HeLin
School: Sichuan Normal University
Course: Condensed Matter Physics
Keywords: First-principles diamond ZrO2 electronic structures opticalproperties
CLC: O469
Type: Master's thesis
Year: 2013
Downloads: 1
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Abstract


At present, LiF crystal and Al2O3crystal usually have been employed as window-materials in shock-wave experiments, but the development of shock-wave experiments needs to explore new window-materials. For this reason, the CASTEP of Materials Studio5.0has been used to investigate the electronic structure and optical properties of the diamond and ZrO2under shock compression.This paper is divided into five chapters. Chapter1tells about the background of this paper, the current situation of experimental and theoretical studies, some questions to be resolved, and the research ideas of the full text. Chapter2will give introduction on the theoretical basis of the first-principles calculation methods and the related software used in the calculations of this paper. Chapter3contents are that the electronic structures and optical properties of diamond without and with vacancy point-defects at255GPa were calculated using first-principles methods, and we analysed the calculation results. Chapter4contents are that electronic structure and optical-absorption property of Zirconia with two crystal structures within the shock-pressure range of95GPa were calculated using first-principles methods, and we analysed the calculation results. Chapter5is the summary and forecast of the full text.The main work and results of this paper are as follows:1. By using CASTEP, the electronic structure and optical properties of diamond perfect-crystal and the crystal with vacancy defect were calculated under shock pressure up to255Gpa. The calculated results show that:at a shock pressure of255GPa, the optical absorption of diamond in the visible-light region is not affected by the shock-induced pressure and temperature; shock-induced vacancy point-defects in diamond crystal cause defective states within the band gap, and the optical absorption induced by the vacancy point-defects appears in the visible-light region of-390-570nm, and in that region there is the transparency loss of diamond. However, in the visible-light region of-570-790nm diamond remains transparent. Effects of shock-induced vacancy-defects on reflectivity and loss-function spectrums are similar: main-spectral peak move slightly toward short-wave region, and their intensity decreases a little.2. By using CASTEP, the electronic structure and optical properties of Z1O2were calculated within the shock-pressure range of95GPa. The results indicate that the shock pressure leads to the blue-shift of the absorption edge in the cubic-phase region but its red-shift in orthorhombic II phase region, whether cubic phase structure or orthorhombic II phase structure ZrO2, the refractive-index increases; the doping causes a band-gap decrease and the red-shift in the cubic-phase region but its increase and the blue-shift in orthorhombic II phase region, CaO doped causes the decrease of the refractive-index. The shock phase-transition may cause a reduction in band gap and the red-shift of the absorption edge, the obvious increase of the refractive-index, the peak value of the reflectivity spectrums declines and moves towards long-wavelength region as well as the energy loss spectrums. The calculated data suggest that within the shock-pressure range of95GPa the CaO-ZrO2can be used as optical window material.The results of this paper have provided theoretical references for shock-wave experiments.

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