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

Abstract

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 D2 molecules out of the Li-Sn slabs in both concentrations of D. With detailed analysis, we unveil a cooperative process of forming D2 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 D2 to nearby Sn atoms. Furthermore, we predict a temperature window in the low concentration case in which D2 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.