Trapping Hydrogen Atoms in Vacancies of Li₂TiO₃ Crystal: A First-Principles Study

The hydrogen atom capacity in the vacancies of the Li₂TiO₃ crystal is systematically studied by the first-principles method to evaluate its tritium release performance as a solid breeder material in nuclear fusion reactors. The adsorption process of adding hydrogen atoms one by one in the vacancy are investigated to find the possible adsorption sites of the hydrogen atoms in the vacancy. The charge transfer and density of states analysis are performed to reveal the form of a hydrogen-hydrogen dimer in the vacancy. Also, the trapping energy and formation energy are defined and calculated to determine the hydrogen atom capacity of the system. According to the simulations, the Ti vacancies have the strongest hydrogen atom capacity followed by Li vacancies, and O vacancies are the weakest. The influence of hydrostatic pressure on the hydrogen atom capacity is also investigated. Our results reveal the hydrogen capacity of vacancies in the Li₂TiO₃ crystal from the atomic scale, which also provide a theoretical guide to the related tritium release experiments.