On the self interstitial atom interactions in metals and their study

The determination of self-interstitial atomic defect interaction radii Ri from recovery experiments after electron irradiation is re-examined in the light of the recent results obtained in Jülich, with particular attention paid to interstitial-defect interactions. The possible sources of errors are mainly neglect of impurity effects, of electrical size effect and casually adapted treatment of the data. The latter point is emphasized. It comes to light that in simple processes with a unique mobile species—as in Al—the possible error on Ri may not affect estimates of Rr , the impurity interstitial trapping radius. Such is not the case if the process is complex as in Cu. Moreover, the analytical expressions given allow easy quantitative estimates of Ri and Rr from experiments on very pure metals and very dilute alloys. It is shown that in the metals studied so far, namely Al, Cu and Pt, the interaction radii to form a di-interstitial atom are about equal in units of annihilation radii. The extreme importance of technical details such as proper specimen handling and treatment looms up.