Positron States in Dislocations: Shallow and Deep Traps

Structures of edge dislocations in aluminum are calculated using molecular dynamics and an effective medium theory with many-atom interactions. The local density approximation is used to calculate the positron states at different trapping sites. The partial [211]-dislocation is a very shallow trap with a positron binding energy of less than 80 meV and a positron lifetime similar to the bulk lifetime. Vacancies and single jogs at the dislocation line result in a lifetime of about 224 ps which is in a good agreement with the experimentally observed lifetimes in aluminum containing dislocations.