Grain boundary sliding and migration in copper: the effect of vacancies

The atomic structure and mechanism of the interface sliding of the Σ = 5(2 1 0)[0 0 1] symmetric tilt grain boundary (GB) in copper and its interaction with vacancies at an elevated temperature has been studied using a computationally efficient potential based on the Embedding Atom Method in connection with the finite temperature Monte Carlo technique. Grain boundary sliding is performed for pure copper as well as copper containing a vacancy at a selected position. The discontinuous changes of the GB energy at certain sliding distances are associated with GB migrations. Elevated temperature reduces the grain boundary sliding/migration energy by a factor of about 2 but does not increase the rate of migration. Migration of the GB is mediated by the flow of atoms along the interface in coordination with the atoms in bulk. The sliding and migration properties partially depend on the position of the vacancy in the GB core. We found that the grain boundary sliding energy profile in the presence of a vacancy placed at the interface increased the GB energy, but reduces the sliding energy. The sliding process invokes the interface migration in such a way that the vacancy effectively migrates to a more convenient position and reduces the GB energy.