Retention and recycling of deuterium in liquid lithium-tin slab studied by first-principles molecular dynamics

Understanding the retention and recycling of hydrogen isotopes in liquid metal plasma-facing materials such as liquid Li, Sn, and Li-Sn are of fundamental importance in designing magnetically confined fusion reactors. We perform first-principles molecules dynamics simulations of liquid Li-Sn slab with inserted D atoms to provide microscopic insights into the interactions of D with Li-Sn liquid metal. We prepare two samples with low and high concentrations of D atoms. We observe evaporation of D molecules out of the Li-Sn slabs in both concentrations of D. With detailed analysis, we unveil a cooperative process of forming D-2 molecules in liquid Li-Sn, where Li atoms act as catalytic centers to trap a D atom before another D comes nearby to form a molecule, and the surplus charges are transferred from D-2 to nearby Sn atoms. Furthermore, we predict a temperature window in the low concentration case in which D-2 molecules can escape to vacuum, while LiD molecules cannot. The above findings deepen our understanding of interactions between hydrogen isotopes and Li-Sn liquid metal. (C) 2020 Elsevier B.V. All rights reserved.