Abstract
Li2TiO3 is one of the most significant breeder materials and has potential applications in future fusion reactors. Defect models with three types of lithium vacancies were considered to study the diffusion behavior of tritium in Li2TiO3 by the density functional theory calculations. The possible tritium adsorption sites inside the lithium vacancy were examined and analyzed. The energy barrier of all diffusion paths between different adsorption sites was calculated and the minimum energy barrier is about 0.45 eV, which indicates that the tritium atom diffuses freely inside the lithium vacancy; when a tritium diffuses across the crystal in the typical three directions, our results reveal that the tritium atom prefers to move along the [010] direction. Furthermore, we found that the minimum energy barrier for the tritium atom to escape the trap of Li vacancy is 0.76 eV. After the tritium jumping out of the Li vacancy, the minimum energy barrier is 0.5 eV for the tritium atom diffusing in the crystal. Therefore, we predict that tritium can easily escape from the trap of the Li vacancy and then diffuse across the crystal. Such results are beneficial to the tritium release process in Li2TiO3 and could provide theoretical guidance for the future applications of the Li2TiO3 materials.
Highlights
Nuclear fusion is a attractive clean energy source with low carbon emission in comparison with today’s conventional energy sources of coal and petroleum
Formation Energy of Lithium Vacancy β-phase Li2 TiO3 was considered a stable phase until 1215 ◦ C, and its crystal structure was first determined by Lang [28] and subsequently refined using X-ray diffraction of large single crystals by Kataoka et al [29]
Based on the calculated formation energies, adsorption energies, and electronic structures of the tritium trapped system, possible tritium adsorption sites inside the lithium vacancy were studied in detail and adsorption sites with minimum adsorption energy were determined firstly
Summary
Nuclear fusion is a attractive clean energy source with low carbon emission in comparison with today’s conventional energy sources of coal and petroleum. A number of lithium ceramic breeder materials are being investigated both theoretically and experimentally, including Li2 O, Li2 TiO3 , Li3 TaO4 , Li2 ZrO3 , Li2 SiO3 , and Li4 SiO4 [3,4] Among these potential tritium breeders, Li2 TiO3 is considered as a candidate material because of its easy reprocessing, low activation, high lithium atom density, compatibility with structural materials, etc. Considering the tritium release process of Li2 TiO3 , tritium diffusion in crystal grains has been shown to be an important step It is affected by various irradiation-induced defects (lithium vacancy, oxygen vacancy, and broken bond). Energy barrier, and electronic structure of tritium with all types of lithium vacancies in Li2 TiO3 are calculated and analyzed systematically These theoretical calculations of tritium diffusion in lithium vacancy of Li2 TiO3 are of prime importance for the understanding of tritium behavior in. Li2 TiO3 and design of the tritium breeding blanket
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