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 SFTs have been studied using computer simulation and a long-range pair potential 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 is the number of vacancies) may change during its growth and the loop can transform, 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 intermediate configurations of a partly dissociated loop. The problem of estimation the binding energy of a vacancy in a VL or SFT as a function of their size has been discussed and several approximations have been tested. Furthermore, the thermal stability of small VLs of different shapes has been studied by molecular dynamics and the VL-to-SFT transformation has been observed.