Tritium species diffusion on and desorption from gamma-LiAlO2(100) surface: A first-principles investigation

摘要

gamma-LiAlO2 enriched in the Li-6 isotope is a good candidate for tritium (T, H-3) production in nuclear reactor. To better understand its H-3 production performance, first-principles calculations are performed to study the H-3-related species diffusion on and desorption from the gamma-LiAlO2 (100) surface. For the diffusion process, we investigate the pathways and energy barriers for the T and OT diffusion on the pristine and defective gamma-LiAlO2 (100) surfaces. Our results reveal that the O and Li/Al atoms of the surface layer play important roles for T and OT diffusion, respectively. By comparing with its diffusion barrier in bulk gamma-LiAlO2, the order of energy barrier for T diffusion is: bulk < surface < defective surface, which is reversed for OT diffusion. Space is the prime factor for OT diffusion, while diffusion-mediating atom instead of space becomes the key factor for T diffusion. For the desorption process, we investigate the H-3-related species (T, OT, T-2, and T2O) desorption from the gamma-LiAlO2 (100) surface. The desorption energies we obtained are so high that the desorption behavior of all the H-3-related species is nearly prohibited. We expect the possible T-2 or T2O release from the large accumulation of H-3 atoms on the surface. (C) 2020 Elsevier B.V. All rights reserved.