The effect of collision cascades upon pre-existing point defects in crystalline materials was studied by simulating 5keV collision cascades in Au, Cu, Al, Pt and Si. The results indicated that collision cascades did not significantly affect interstitials or vacancies outside of the liquid core of the cascade although, in the face-centered cubic metals, heating of the crystal due to the cascade caused some thermal migration of the interstitials. Within the liquid cascade core, both interstitials and vacancies moved towards the center of the molten region when it resolidified, and recombined or clustered there. At high temperatures, random jumps of interstitials during the thermal-spike phase could cause significant additional trapping of interstitials in the liquid. In contrast to the annealing effects of pre-existing damage in face-centered cubic metals, the amount of new damage in Si which was created by a cascade was roughly independent of the number of initial point defects. The difference was attributed to the nature of the bonding in the materials.

K.Nordlund, R.S.Averback: Physical Review B, 1997, 56[5], 2421-31