PNNL

Abstract

A systematic molecular dynamics study of the diffusion mechanisms of He interstitial and their small clusters at two representative interfaces, sigma11 and sigma3, has been carried out in alpha-Fe. The diffusion coefficient of a He interstitial and the effective migration energies were determined, and the diffusion mechanisms of single interstitials and di-He interstitials are discussed in detail. A di-He interstitial cluster can kick out a self interstitial atom (SIA) at high temperatures, forming a He2V complex. The SIA migrates rapidly near interfaces, whereas the He2V complex is immobile at the temperatures considered. This small cluster may serve as a smallest nucleation for the formation of helium bubbles at interfaces.