Stability and mobility of defect clusters and dislocation loops in metals

According to the production bias model, glissile defect clusters and small dislocation loops play an important role in the microstructural evolution d uring irradiation under cascade damage conditions. The atomic scale compute r simulations carried out in recent years have clarified many questions abo ut the structure and properties of glissile clusters of self-interstitial a toms that are formed directly in the cascade volume. It has been found that such clusters consist of sets of crowdions and are highly mobile in the cr owdion direction. Very recently, one-dimensional glide of similar character has been observed in the computer simulation of small vacancy loops in alp ha-Fe. In the present paper we summarise results obtained by molecular dyna mics simulations of defect clusters and small dislocation loops in alpha-Fe (bcc) and Cu(fcc). The structure and stability of vacancy and interstitial loops are reviewed, and the dynamics of glissile clusters assessed. The rel evance and importance of these results in establishing a better understandi ng of the observed differences in the damage accumulation behaviour between bcc and fee metals irradiated under cascade damage conditions are pointed out. (C) 2000 Elsevier Science B.V. All rights reserved.