Vacancy loops and stacking-fault tetrahedra in copper - II. Growth, shrinkage, interactions with point defects and thermal stability

The interaction of vacancy loops (VLs) and stacking-fault tetrahedra (SFTs) with point defects and the processes of growth and shrinkage of VLs and SF Ts have been studied using computer simulation and a long-range pair potent ial for copper. It was found that there is a qualitative difference in the mechanism of growth of VLs and SFTs. While VLs can grow without limitations , the growth of SFTs containing more than 91 vacancies is rather difficult. The structure of small vacancy loops (N-v less than or equal to 217; N-v i s the number of vacancies) may change during its growth and the loop can tr ansform, in turn, to a completely dissociated loop with six small truncated SFTs, a faulted Frank loop with Burgers vector b = 1/3(111) and several in termediate configurations of a partly dissociated loop. The problem of esti mation the binding energy of a vacancy in a VL or SFT as a function of thei r size has been discussed and several approximations have been tested. Furt hermore, the thermal stability of small VLs of different shapes has been st udied by molecular dynamics and the VL-to-SFT transformation has been obser ved.