Structure of grain boundaries in nanocrystalline palladium by molecular dynamics simulation

The grain boundaries (GB) in nanocrystalline Pd with high-energy bicrystalline GB are compared. The appearance upon annealing or growth from the melt of a highly disordered GB of uniform thickness and energy is driven by lowering of the GB energy and represents a thermodynamic-equilibrium phenomenon. The random misorientations between the grains give rise to GBs having both tilt and twist components and a relatively high energy. The main difference between the GBs in a coarse-grained and a nanocrystalline microstructure lie in their respective GB energy distribution. Coarse-grained materials exhibit a broad, more equilibrated GB-energy distribution while a nanocrystalline microstructure with random grain orientations contain only high-energy GBs.