Evolution of the Chemical Content of the Oxidized Li Surface Under Hydrogen Bombardment

The lithium coated plasma-material interfaces could quickly oxidize to form lithium-oxide, Li₂O, and lithium-hydroxide, LiOH, owing to the presence of oxygen from oxide components and oxidized metal PFCs, as well as due to the presence of water in the background gas of the vacuum vessel. We have recently published molecular dynamics results [1] for sputtering and reflection from Li based compounds irradiated by hydrogen showing that the low energy range of impact energies (< 100 eV) produces a variety of unexpected effects. The present molecular dynamics study is undertaken to understand the changes of the chemical structure of the PFCs material by cumulative H irradiation on the Li oxidized materials and take initial steps in predicting the best ratio of Li, O and H for the lowest recycling. We find that it is important to use reactive classical potentials equipped with ability to accurately consider polarization and charging of the interacting atoms, due to their low (Li) and high (O) electronegativity with respect to H, followed by verification of the results using quantum - classical molecular dynamics. Very complex chemistry emerges upon impinging hydrogen atoms into oxidized Li surface, with changing of the reaction mechanisms depending on the initial structure and instantaneous ratio of Li, O and H in the PFC.



1. P.S. Krstic et al, Front. Phys. 11, 8 (2023) and references therein.