Molecular dynamics simulations of displacement cascade and threshold energy in ordered alloy Al3U

Abstract

The displacement threshold energy and collision cascades in ordered alloy Al3U with L12 structure are studied by molecular dynamics simulations. It turns out that as compared with Al recoils, U primary recoils generally have a lower average displacement threshold energy Ed (i.e. 41 eV vs 20 eV) and show less crystallographic anisotropy. The [1 1 0] direction which can produced a …-U-Al-U-Al… replacement collision sequence is found to have a high Ed, but does not create a long antisite defect chain. We have simulated 100 cascades with different energies of primary knock-on atom (PKA) ranging from 1 to 5 keV to make clear which role the energy, direction and PKA’s species has played on defect production. The number of surviving stable defects has a power-law dependence on energy. Displacement cascades tend to form large size clusters involving many point defects with increasing PKA’s energy, and the U PKA generally forms clusters with size larger than the Al recoil.