Calculations were made of the positron trapping efficiency, at vacancies and their clusters, at the transition limit of the optical potential approach. The results were compared with those of an approach which was based upon Fermi’s golden rule. No significant differences were found for metals or semiconductors. The calculations showed that elastic scattering of positrons at vacancies and their clusters was more important than trapping.

J.Dryzek: Journal of Physics - Condensed Matter, 1995, 7[29], L383-92