PNNL

Abstract

Molecular dynamics *MD* methods are utilized to study the formation of vacancy clusters created by displacement cascades in *-Fe containing different concentrations of substitutional He atoms.Primary knock-on atom energies, Ep, from 500 eV to 20 keV are considered at a temperature of 100 K, and the results are compared with those performed in pure *-Fe. There are distinct differences in the number and size of vacancy clusters within displacement cascades with and without substitutional helium atoms. It is found that many large vacancy clusters can be formed within cascade cores in *-Fe with helium atoms, in contrast to a few small vacancy clusters observed in pure *-Fe. The number and size of helium/vacancy clusters generally increase with increasing helium concentration and PKA energy. One of the striking results is that the number of self-interstitial atoms *SIAs* and the size of interstitial clusters are much smaller than those in pure *-Fe.