Ta concentration effect on nucleation of defects in W-Ta alloy from first-principles model

Tungsten alloys are candidates for materials in DEMO diverter applications due to their excellent thermal and mechanical properties. Using the first-principles method, we researched the effect of Ta concentration on the nucleation of vacancy and self-interstitial atom clusters to better understand the evolution of defect behaviours in W-Ta alloys. Our calculation results indicate that Ta atoms can not only effectively inhibit the formation of mono-vacancy, but also hinder the nucleation of vacancy clusters. The magnitude of this interaction on vacancies would be more obvious with increasing Ta atom concentration. In addition, the study of "nSIA-mTa" structures indicates that the Ta atom can obstruct the nucleation of the SIA cluster, but competition exists between SIAs and the Ta concentration. The diffusion behaviours of <111>dumbbell have been researched using the CI-NEB method, indicating that Ta can slow down the diffusion of W-SIA by compelling it to change the diffusion direction. Therefore, it is conjectured that the Ta atom can effectively promote the recombination rate of the Frenkel pairs, resulting in an enhancement of defect self-repair of W-Ta alloy materials under neutron irradiation.