Effect of transmutation elements Re and Ta on the vacancy formation and dissociation behaviors in W bulk

摘要

Transmutation elements are the essential products induced by high energy neutron radiation in plasma facing materials tungsten, which would bring the further effects on their point defects' evolutions and service performance. Here, transmutation elements Re and Ta atom have been selected to assess the effects on vacancy and vacancy cluster in W material via first-principles calculations. The formation energy indicates mono-vacancy is more likely to form in W-Re system than pure W and W-Ta system. Both Re and Ta will reduce the diffusion barriers for the mono-vacancy migrations. The present calculations indicate that vacancy cluster is more inclined to grow up via combining the vacancy cluster rather than a single mono-vacancy. Re is favorable to the nucleation and growth of vacancy clusters, while Ta has a suppressive effect on the aggregation of small vacancy clusters. The emphasis analysis is obtained according the volumetric dependent strain. Vacancy dissociation calculations show that the dissociation of vacancy clusters is easier to begin with a single vacancy dissociation process.