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Homogeneous bulk, surface, and edge nucleation in crystalline nanodroplets

Kari Dalnoki-Veress McMaster University, Canada

The birth of a crystal is initiated by a nucleus from which the crystal grows—a dust grain
in a snowflake is a familiar example. These nuclei can be heterogeneous defects, like
the dust grain, or homogeneous nuclei which are intrinsic to the material. I will present a recent study of homogeneous nucleation in nanoscale polymer droplets on a substrate which itself can be crystalline or amorphous. Droplets are an ideal confining geometry because the length scales can be easily controlled and it is possible to arrange the system such that each droplet acts as an independent experiment. We observe a large difference in the nucleating ability of the substrate. Furthermore, the scaling dependence of nucleation on the size of the droplets proves that the birth of the crystalline state can be directed to originate predominantly within the bulk, at the substrate surface, or at the dropletʼs edge, depending on how we tune the substrate.