Time: 4:00 p.m.
Place: ICAMS Seminar room IC 02-718
Yunzhi Wang, Department of Materials Science and Engineering, The Ohio State University, Columbus, USA
Even though more than six decades have passed since the first theory on hetero-geneous nucleation (HN) at grain boundaries (GBs) was established in the 1950s, the concurrent shape variation (co-deformation) of both the nucleus and the GB was not captured by existing models. By using a fully variational approach, where orientation relationships between the product and parent crystals and interaction between low-energy interface facets on the nucleus and the GB plane are consid-ered simultaneously, we demonstrate for the first time the effect of interface co-deformation on the fundamental properties of a critical nucleus. Without any a pri-ori constraints on the shapes of the critical nucleus and the GB surface, our calcula-tions show that a nucleus is highly deformable in response to its interaction with the GB along the triple junction line. Consequently, its energy of formation can be reduced by orders of magnitude relative to predictions by previous methods.