First-principles study of the energetics of Fe interstitial clusters in vanadium

Abstract

The energetics of Fe interstitials and their clusters as well as the effect of Fe on the migration of self-interstitial (SIA) and vacancies in vanadium (V) are investigated by first-principles calculations. We determined the formation energies of mono-/di- Fe-V and Fe-Fe interstitial pairs by typical structures (<111>, <110> and <100>), and found that the <110>Fe-Fe and mixed <111>Fe-V dumbbell are the lowest energy configuration. Secondly, we determined the formation/binding energies of small Fe-Fe/Fe-V interstitial clusters with sizes of 3–6. The binding energies of clusters increase with sizes from 0.69 to 4.62 eV. The interstitial clusters tend to form three-dimensional parallel configurations and the parallel <111> configurations are the most stable. By comparison, the <111>Fe-Fe clusters are more stable than both mixed Fe-V and SIA clusters. Moreover, we explored the effect of Fe on the formation and migration of SIAs/vacancies. Fe increases defect formation energy and changes rotation barrier of SIA. The migration barrier of SIAs near Fe is still very small along <111> direction, and the SIAs near compressed Fe can transform into mixed Fe-V pair with a low barrier of 0.01 eV. Vacancy migrating towards Fe exhibits a higher barrier of 0.52/0.54 eV than that of 0.39 eV in pure V, while the barrier of vacancy exchanging Fe is very high of about 1.05 eV.