The anisotropy and temperature dependence of the threshold energy for radiation damage in gold - comparison with other fcc metals

The growth behaviour of interstitial-type dislocation loops in Au as observed in a high-voltage electron microscope is used to determine the anisotropy and temperature dependence of the threshold energy for atom displacement, Ed. At 473 K minima of Ed are found in the <100> (17.5 eV) and the <110> (21 eV) directions. Au is thus the first fcc metal in which the absolute minimum of the threshold surface has been established not to lie in or close to the <110> direction. A comparison of the threshold-energy data of fcc metals leads to the conclusion that the reason for the 'anomalous' behaviour of Au is to be found in the exceptionally large ratio of ionic radius to lattice parameter. In a discussion of the temperature dependence of Ed it is shown that the rather strong reduction of the threshold energies in or near the <111> directions at elevated temperatures may be explained in terms of the 'window-opening' mechanism. (orig.)