Collaborative Motion of Helium and Self-Interstitial Atoms Enhanced Self-Healing Efficiency of Irradiation-Induced Defects in Tungsten

Abstract

The self-healing of nuclear materials is dependent on the motion pattern of irradiation-induced defects. Helium (He) is a typical impurity element in nuclear materials and plays a crucial role on the microstructure evolution under irradiation. Here, we systematically investigate the interactions of He with self-interstitial atoms (SIAs) in tungsten (W) as well as their influences on the kinetic behaviors of SIAs and defects annihilation, using first-principles method and object kinetic Monte Carlo calculations. It is found that there are attractive interactions between He and SIAs, which become stronger with the increasing of SIA numbers. Therefore, He has significant effect on the migration behaviors of SIAs in W. Specifically, the He-SIA1 and He-SIA2 complexes adopt a three-dimensional (3D) migration pattern with the energy barrier of 0.38 and 0.61 eV, respectively, which is completely different from the fast 1D migration of SIAs in W (≤ 0.033 eV) without He. Such unexpected collaborative 3D motion of He-SIA complexes increases the probability of Frenkel pairs recombination and reduces the number of surviving defects. Consequently, our calculations reveal the enhancing effect of He on the self-healing efficiency in W, governed by the concerted 3D motion of He-SIA complexes. These will improve our fundamental understanding of the influence of impurities on the evolution of irradiation defects in nuclear materials.