The origin of the long-range correlated jumps observed in molecular-dynamics simulations of Brownian motion of interstitial clusters in irradiated crystalline materials was investigated. It was shown that the presence of long jumps was associated with the low thermal friction experienced by a cluster propagating through the crystal lattice in the presence of thermal fluctuations. By using the equation for the friction coefficient, the lengths of the ballistic trajectories of clusters ejected from high-energy cascades were estimated. The implications of the findings were analyzed with regard to an understanding of the nature of the long-range effects observed in experiments on the ion implantation of face-centered cubic and body-centered cubic metals, and the connection between this effect and the stability of metals under irradiation.

Thermal Friction and Brownian Motion of Interstitial Defects in Irradiated Materials. S.L.Dudarev: Journal of Nuclear Materials, 2002, 307-311[2], 881-5