Correlated Collisions in a Displacement Spike

The influence of correlated collisions due to lattice structure is investigated for f.c.c. lattices and discussed in detail for Cu. The model used is that of Silsbee in which the assumed exponential potential between atoms gives approximately hard core collisions. Two possibilities which may cause long-range effects are investigated; (1) focusing collisions which are suggested not to effect an interstitial transport. (2) crowdion-like collisions with interstitial transport. The number of such collisions as well as their range is calculated for given energy of a primary knock on. The result shows that the range should be determined by the focusing collisions only. The theoretical range (about 100 atom spacings) is in agreement with the experimental value derived out of the damping experiments in Cu. The effect of crowdion collisions on disordering is discussed for Cu3Au.