Helium diffusion behavior and its retention in LaNiAl alloy from molecular dynamic simulations

Molecular dynamic method has been used to investigate the diffusion behavior of helium atom in the LaNiAl alloy system. The results have shown that diffusion coefficient of helium atom increases as the temperature increases from 300 to 1500 K, which indicates that helium atom gets more active via thermal desorption. The diffusion coefficient in LaNi5 and LaNi4Al are about 1.5 × 10−5 and 1.1 × 10−6 cm2/s at 1300 K, respectively, and the diffusion barrier of He are 1.45 and 0.52 eV, respectively. The helium diffusion is shown to be enhanced with temperature increasing. Compared with metallic La, Ni, Al and Pd, the simulation result implies that helium atom is more stable and difficult to diffuse in LaNi5 and LaNi4Al alloys, which are the most promising materials for helium retention in experiments. Our results indicate the correlation between diffusion behavior of helium atom and capacity of materials for helium retention. Therefore, it can be considered as a feasible method to evaluate the helium retention capacity of materials via determining the diffusion properties of interstitial helium atom.