  The thermodynamics and kinetics of crystallization of nanoparticles, as
opposed to bulk phases, may be influenced by surface and size effects. We
investigate the importance of such factors in the crystallization process of
gold, silver, and iron nanodroplets using numerical simulations in the form of
molecular dynamics combined with path sampling. This modeling strategy is
targeted at obtaining representative ensembles of structures located at the
transition state of the crystallization process. A structural analysis of the
transition state ensembles reveals that both the average size and location of
the critical nucleation cluster are influenced by surface and nanoscale size
effets. Furthermore, we also show that transition state structures in smaller
nanodroplets exhibit a more ordered liquid phase, and differentiating between a
well-ordered critical cluster and its surrounding disordered liquid phase
becomes less evident. All in all, these findings demonstrate that
crystallization mechanisms in nanoparticles go beyond the assumptions of
classical nucleation theory.
