First-Principles Study of Tritium Diffusion in the LiTaO Crystal.

LiTaO with a high melting point, good thermal stability, and higher lithium content has become a possible choice for breeder materials, which have potential applications in future fusion reactors. Perfect and defect crystal models of LiTaO are set up, and all of the tritium-diffusion pathways have been studied by the first-principles method. The activation energy barriers of different diffusion pathways are calculated and analyzed considering the pathway length and tritium-oxygen interactions. The obtained minimum energy barrier for tritium diffusing in the perfect LiTaO crystal is only 0.34 eV. The minimum energy barrier is less than 0.72 eV when tritium diffuses in the defect LiTaO crystal in the presence of a lithium vacancy. Finally, the diffusion coefficients of tritium in the LiTaO crystal are calculated, which further confirm that it is easy for tritium to escape from the trap of the lithium vacancy and diffuse in the crystal. Such a tritium-diffusion behavior is in favor of the tritium-release process of the LiTaO crystal and could provide theoretical guidance for the future applications of LiTaO materials.