Computer molecular-dynamics studies of grain-boundary structures. I. Observations of coupled sliding and migration in a three-dimensional simulation

Methods of computer molecular dynamics have been applied to model a 𝒥 = 5 symmetric-tilt coincidence grain boundary. A pairwise Lennard-Jones 6–12 potential was used to simulate the atomic interactions in a bicrystal containing up to 396 atoms. At simulated temperatures of approximately half the potential well depth the boundary undergoes spontaneous sliding coupled with migration. The observations are consistent with a geometrical model based on the coincidence model of grain boundaries and also with the results of a separate calculation of the Peierls-Nabarro-like energy barrier for such coupled sliding and migration, using a static relaxation method on a model constrained to have various displacements.