Synergistic influence of dislocations and helium cluster on hydrogen atom in tungsten

Dislocations are common line defects in the preparation and irradiation processes of tungsten (W), and they can serve as trapping sites for hydrogen (H) and helium (He) atoms. Existing studies have indicated that dislocations preferentially capture He atoms to form dislocation-He cluster structures. The focus of this study was on the effects of this new structure on the trapped and diffusion behavior of H atoms using molecular dynamics (MD) method. The study considered the number of He atoms from 1 to 150, and they were classified as small He cluster and large He cluster. By calculating the binding energy, the study revealed that the capture strength is positively correlated with the He clusters' size. However, it is negatively correlated with the distance from the dislocation core and the captured H atoms' number. This study output the stable configurations to analyze the growth patterns of He cluster in dislocations, and it was observed that the interstitial atoms caused by trap mutation preferentially aggregate into dislocation loops due to the dislocation core structure. Moreover, the study investigated the diffusion behavior of H atoms around the dislocation-He cluster structure at 600 K within 1 ns. The hydrogen atoms tend to migrate towards the He cluster and distribute around it uniformly. The distribution range narrows with the helium cluster's size, and the distribution pattern depends on the dislocations' type. This demonstrated the formation of dislocation-He cluster structure, promoting the increased H retention.