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From electronic structure of point defects to physical properties of complex materials using atomic-level simulations.

机译:从点缺陷的电子结构到使用原子级模拟的复杂材料的物理特性。

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摘要

Point defects play a significant role in determining the physical and chemical properties of materials. Atomic-level simulation is a powerful tool to investigate and characterize the effect of these point defects. In this study, various aspect of the structure and stability of complex materials have been determined and predicted for lithium niobate, ceria-based systems, and titanium. The production, evolution, and dynamic behavior of defects have been explored. The focus has been on establishing the relationship between point defects and fundamental properties of bulk materials.;Lithium niobate is an important ferroelectric and non-linear optical material. For lithium niobate, the dominant defects with the lowest formation energies and their equilibrium structures are predicted under various experimental relevant environments. The site preferences with corresponding charge compensation mechanisms are compared with experimental observations. The diffusion mechanism and energy barrier are determined to elucidate the dynamic behavior of defect and defect clusters. The effects of point defects on the polarization of the system are also discussed.;Ceria-based systems are considered as potential electrolytes of solid oxide fuel cells. In ceria-based systems, the effects of sub-stoichiometry, temperature and ionic radii on the mechanical properties are evaluated using molecular dynamics simulation. It is observed that sub-stoichiometry lead to a significant softening of the elastic constants. Similar results are predicted for doped ceria systems. These softening effects arise from the significantly reduced strength of ionic interactions.;Titanium is a candidate material for cladding of fast nuclear reactor system due to its high corrosion resistance and excellent mechanical properties. In this study, cascade simulations are carried out to investigate its radiation resistance. The effect of a high-energy atom (primary knock-on atom) is simulated with various energies, positions and orientations. A high disordered region with a large number of point defects is observed during the initial phases of simulations (ballistic phase), followed by recombination of interstitials and vacancies (relaxation phase). The effects of primary knock-on atom energies on remnant defects are established. The orientation effects of primary knock-on atom and the effects of grain boundaries are also evaluated.
机译:点缺陷在确定材料的物理和化学性质中起着重要作用。原子级仿真是研究和表征这些点缺陷影响的强大工具。在这项研究中,已经确定并预测了铌酸锂,二氧化铈基体系和钛的复杂材料的结构和稳定性的各个方面。已经探究了缺陷的产生,演变和动态行为。焦点一直放在建立点缺陷与块状材料基本性能之间的关系上。铌酸锂是一种重要的铁电和非线性光学材料。对于铌酸锂,在各种实验相关环境下,预测了具有最低形成能的主要缺陷及其平衡结构。将具有相应电荷补偿机制的位点偏好与实验观察结果进行比较。确定扩散机理和能垒,以阐明缺陷和缺陷簇的动态行为。还讨论了点缺陷对系统极化的影响。基于二氧化铈的系统被认为是固体氧化物燃料电池的潜在电解质。在基于二氧化铈的系统中,使用分子动力学模拟评估了亚化学计量,温度和离子半径对机械性能的影响。观察到亚化学计量关系导致弹性常数的显着软化。对于掺杂的二氧化铈系统,预计会有类似的结果。这些软化作用是由于离子相互作用强度的显着降低引起的。钛由于其高耐腐蚀性和优异的机械性能而成为快速核反应堆系统覆层的候选材料。在这项研究中,进行了级联模拟以研究其抗辐射性。用各种能量,位置和方向模拟高能原子(主敲除原子)的作用。在模拟的初始阶段(弹道阶段),随后是间隙和空位的重新组合(松弛阶段),观察到具有大量点缺陷的高无序区域。建立了初级敲除原子能量对残余缺陷的影响。还评估了初级敲除原子的取向效应和晶界的影响。

著录项

  • 作者

    Xu, Haixuan.;

  • 作者单位

    University of Florida.;

  • 授予单位 University of Florida.;
  • 学科 Physics, Solid State.;Physics, Condensed Matter.;Engineering, Materials Science.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 194 p.
  • 总页数 194
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 ;
  • 原文服务方 国家工程技术数字图书馆
  • 关键词

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