Embedded-atom study of low-energy equilibrium triple junction structures and energies

We present an atomistic study of the structures and defect energies of triple junctions (TJs) in polycrystalline materials. A new concept to calculate the excess energy of isolated TJs is proposed and applied to a molecular dynamics (MD) study of iron tricrystals. Line energies of bulk TJs (merging three grain boundaries (GBs)) and surface TJs (merging one grain boundary and two surfaces) are found to be very low. In absolute value they amont to only a few 10−10 Jm−1. Remarkably, defined as a correct excess energy relative to the GBs, the bulk TJ energy is determined to be negative in all studied configurations with an average value of −2.8 × 10−10 Jm−1. These quantitative results are in contrast to various experimental attempts, but they fully agree with simple geometric estimates and broken-bond models, which prompts a re-interpretation of reported measurements. [Display omitted]