A DFT + U study on diffusion and aggregation behavior of He atoms in Li₂TiO₃

Future fusion power plants are designed based on the deuterium-tritium fusion reactions. Yet, as an element with a half-life of 12.5 years, tritium cannot be obtained in large quantities from nature. To meet future demand, an artificial nuclear reaction is needed to use tritium breeder materials to produce tritium. At present, Li₂TiO₃ is the most promising tritium breeder blanket material in fusion reactor. The existing experimental results show that helium irradiation will change the crystal structure of Li₂TiO₃ and cause embrittlement failure. In order to study the microscopic helium embrittlement mechanism of Li₂TiO₃, the diffusion and aggregation behavior of helium atoms in Li₂TiO₃ bulk was calculated by first principles. The reasons for the formation of the most stable interstitial configuration of helium atoms and helium clusters in Li₂TiO₃ bulk are explained by lattice vibrational theory and electronic structure analysis. At the same time, the relatively new research results in this work are mainly as follows: In Li₂TiO₃ bulk, the three spatial inversion symmetries Li vacancy helium atoms tend to diffuse from all Li vacancies to Li₂ vacancies. Meanwhile, the Li₂ vacancy is the most likely site for helium clusters to nucleate. And helium atoms and the helium clusters tend to arrange and grow along the plane of the Li layer. © 2023 Elsevier B.V.