Trapping and recombination of tritium in lithium vacancy of the γ-LiAlO2 (100) surface: A first-principles study

γ-LiAlO2 is an important tritium (T, 3H) breeding material in fusion reactors. To explore the possible products of 3H species from the most stable γ-LiAlO2 (100) surface, first-principles calculations are performed to study the trapping and recombination of 3H in the surface Li vacancy (VLi). Our results indicate that one and two VLi sites can trap a maximum of two and three 3H atoms, respectively. The 3H accumulation is more preferable with increasing VLi under irradiation. When the 3H atoms are over-accumulated, the 3H atoms can be combined into T2 or T2O molecules. The T2 molecule desorbs spontaneously from the surface even with one VLi. The T2O molecule has an energy barrier of 0.71 eV in desorption, and the O atom in T2O has one coordination that needs at least two Li vacancies formation. Therefore, the T2 molecule should be the main product initially released from the surface. As the number of VLi increases under irradiation, the T2O yield could be increased. Our results provide a better understanding of 3H species released from γ-LiAlO2.