The primary damage state in fcc, bcc and hcp metals as seen in molecular dynamics simulations

Recent progress in the use of molecular dynamics (MD) to investigate the pr imary state of damage due to displacement cascades in metals is reviewed, w ith particular emphasis on the influence of crystal structure. Topics consi dered include the effect on defect formation in pure metals and alloys of p rimary knock-on atom (PKA) energy and irradiation temperature. An earlier e mpirical relationship between the production efficiency of Frenkel pairs an d cascade energy is seen to have wide validity, and the reduction in effici ency with increasing irradiation temperature is small. Crystal structure ha s little effect on the defect number. In terms of the development of models to describe the evolution of radiation damage and its role in irradiation- induced changes in material properties; the important parameters are not on ly the total number of Frenkel defects per cascade but also the distributio n of their population in clusters and the form and mobility of these cluste rs. Self-interstitial atoms form clusters in the cascade process in all met als, and the extent of this clustering does appear to vary from metal to me tal. Vacancy clustering is also variable. The mobility of all clusters depe nds on their dislocation character and thus on the crystal structure and st acking fault energy. It is shown that computer simulation can provide detai led information on the properties of these defects, (C) 2000 Elsevier Scien ce B.V. All rights reserved.