Positron annihilation in helium- and krypton-decorated microvoids in fcc metals

Publisher Website
Google Scholar
Abstract
The electronic structure and positron annihilation characteristics (lifetime and angular correlation between annihilation quanta) in microvoids containing 1, 2, 4, 8, 10, and 13 vacancies in fcc Cu and Al have been calculated using the density-functional formalism and local-density approximation. The positron lifetimes and binding energies are shown to increase with the void size, saturating when voids become big. The positron lifetimes are found to drop sharply when these voids are decorated with rare-gas atoms such as He and Kr. The angular correlation curves are found to broaden when vacancies are decorated with rare-gas atoms with a concomitant decrease in the peak counting rate. The results are compared with recent experiments on He-irradiated Al and Kr-irradiated Cu. Comparison between theoretical and experimental positron lifetimes sheds light on the morphology of defects trapping the positrons. The technological significance of the present study is also pointed out.