Point defect survival and clustering fractions obtained from molecular dynamics simulations of high energy cascades

The evolution of high-energy displacement cascades in iron has been investigated for times up to 200 ps using the method of molecular dynamics simulation. The simulations were carried out using the MOLDY code and a modified version of the many-body interatomic potential developed by Finnis and Sinclair. Previously reported results have been supplemented by a series of 10 keV simulations at 900 K and 20 keV simulations at 100 K. The results indicate that the fraction of the Frenkel pairs escaping in-cascade recombination is somewhat higher and the fraction of the surviving point defects that cluster is lower in iron than in materials such as copper. In particular, vacancy clustering appears to be inhibited in iron. Many of the larger interstitial clusters were observed to exhibit a complex, three-dimensional morphology. The apparent mobility of the [111] crowdion and clusters of [111] crowdions was very high.