Ab initio modelling of helium behavior in α-Fe/TaC interface

Abstract

To understand the role of α-Fe/TaC interface on the clustering behavior of helium (He) atoms inside castable nanostructured alloys under irradiation, we built two models (Ta13C14@Fe215 and {100} 〈110〉 Fe//{100} 〈100〉 TaC interface) and perform systemical ab initio calculations to investigate the energetics of point defects (vacancy, anti-site defect and He), substitutional defect clusters CrFem (1 ≤ m ≤ 4), and Hen (1 ≤ n ≤ 4) clusters, the migration behavior of He atom as well as the effect of Cr atoms and vacancies on the stability of Hen clusters. Vacancy and He at the α-Fe/TaC interface of the Ta13C14@Fe215 are more stable than that in Ta13C14 cluster and Fe matrix. Ta atom at this interface escapes from the lattice site more easily than C atom. In addition, the Cr atoms substituting Fe sites are more stable than Fe vacancies, which reduces the formation energies of Hen clusters in α-Fe/TaC on the Ta13C14@Fe215. Both formation energy and migration energy of He atom in {100} 〈110〉 Fe//{100} 〈100〉 TaC interface are lower than those in bulk TaC and α-Fe. Hence, {100} 〈110〉 Fe//{100} 〈100〉 TaC interface as a sink can trap more helium atoms and vacancies than α-Fe matrix.

Keywords

• Interface
• He
• TaC
• Castable nanostructured alloys