An atomistic study of grain boundary stability and crystal rearrangement using molecular dynamics techniques

The stability of grain boundaries (GBs) and the dynamic behavior of atoms in the boundary region are investigated from an atomistic standpoint. Symmetric and non-symmetric GBs are constructed using an fcc configuration, and the GB energy is calculated as a function of the misorientation angles using a Lennard-Jones-type interatomic potential. Several specific angles are revealed to exhibit cusp-shaped low values. The effect of atomic relaxation at the GB is then simulated, showing a decrease in the GB energy. Changes in the morphology of a grain embedded in a bulk single crystal are also simulated. Using both a square-grain and a circular-grain model, the following results are obtained. In models with small misorientation angles, the grain changes orientation and the GB vanishes. When the orientations are initially stable, no change in the grain is observed. However, in models with non-stable orientations, local stabilization occurs by a rearrangement of the atoms around the GB, and the shape of the grain is transformed. Finally, a similar simulation is carried out at a high temperature, and this reveals that grain contraction occurs even in models that are stable at a low temperature, and that the grain eventually disappears.