Molecular dynamics simulation of low energy displacement cascades in Cu

Molecular dynamics computer simulations have been performed to study properties of low-energy (< 500 eV) displacement cascades in Cu. Various aspects of the time development of cascades are considered including instantaneous number of Frenkel pairs, partitioning of kinetic and potential energies, distribution of atom kinetic energies, cascade expansion rate, and Frenkel pair distributions. The anisotropy of the threshold energy for Frenkel-pair production is interpreted in terms of “branching”. Replacement sequences and the damage function are discussed based on analysis of events corresponding to 18 recoil directions. The damage function exhibits a plateau at $\text{v ~ 0.5}$ Frenkel pairs extending from 25–150 eV; at higher recoil energies the onset of multiple defect production is much slower than predicted by the modified Kinchin-Pease model.