Energetics of Triple Junctions in Polycrystalline Materials

In nanomaterials, defects can govern bulk thermodynamics and properties under dynamic conditions. Specifically, at the finest grain sizes in nanocrystalline alloys, triple line density can reach well above typical dislocation density in polycrystalline materials, and thus can play a significant role in bulk properties as a whole. Hence in this work, we study ensembles of triple junctions in nanocrystalline face-centered cubic metals. The line density is found to correlate with high-angle grain boundary energy and dislocation line energy, although with a negative correlation: triple junctions are thermodynamically favorable defects. In essence, triple line energies are found to be of order -10^-10 J/m which is close to the magnitude of dislocation core energy around ~ -<i>Gb</i>²/12. The method is also demonstrated by the extraction of defect energy from previously published experiments on Se nanocrystals.