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Center for Nonlinear Studies |
Nucleation is the process by which a metastable phase decays into a stable phase. It is widely observed in nature, and is responsible for many phenomena like cloud formation and crystal growth. The classical nucleation theory predicts a compact droplet of the stable phase that will initiate the nucleation process. For many systems with long range interactions, however, the droplets are highly ramified and harder to locate due to lack of a well-defined structure. This has significant implications for material properties. I have been studying nucleation in Lennard-Jones liquids, by performing Molecular Dynamics simulations in a Micro-Canonical ensemble of Argon particles. The system is quenched from liquid temperatures into a metastable solid phase, and allowed to evolve under constant energy dynamics. I investigate the symmetry of the critical nucleus by pinpointing its exact location and time of appearance and employing spherical harmonics to identify the spatial arrangement of molecules. The deeply quenched region far from coexistence exhibits non-compact droplets with structures far removed from the stable fcc phase. This could be an indicator of spinodal nucleation, giving us an idea of the limit of metastability (pseudospinodal).
Host: Chris Neale