Molecular dynamics simulations were made of the displacement cascades created in α-Fe by primary knock-on atoms with energies ranging from 5 to 20keV, and with masses chosen to represent C, Fe and Bi. The knock-on-atom/Fe interaction potential at short ranges was varied, and damage by molecular Bi2 was simulated by using two Bi knock-on atoms. Four effects were reported. Firstly, the knock-on atom mass had a major effect upon the damage produced in individual cascades, while the knock-on-atom/Fe potential had little influence. Secondly, the total number of point defects produced in a cascade decreased with increasing knock-on atom mass. This fact was not accounted for by the other models used to estimate damage. Thirdly, interstitial loops of ½<111>-type, and both vacancy and interstitial loops of <100>-type, were formed; the latter being observed for the first time in a molecular dynamics simulation. The probability of appearance of <100>-loops increased with increasing knock-on-atom mass, as well as energy. Finally, there was a correlation between the production of large vacancy clusters and interstitial clusters within the same cascade.

Effect of Mass of the Primary Knock-On Atom on Displacement Cascade Debris in α-Iron. A.F.Calder, D.J.Bacon, A.V.Barashev, Y.N.Osetsky: Philosophical Magazine Letters, 2008, 88[1], 43-53