Enhanced sampling techniques such as well-tempered metadynamics can provide insights into processes that are not easily accessible via conventional molecular dynamics (MD). We explore the application of a collective variable derived from the Debye scattering function to examine amorphous-crystalline phase transitions in several model systems. To support the physical insight of such an approach, we contrast the mechanistic details and kinetic barriers of the resulting crystallization pathway with corresponding traditional (unbiased) MD simulation. In each case, we find that the collective variable correlates strongly with the largest crystalline cluster size during the phase transition, suggesting that both the biased and unbiased approaches yield similar mechanisms. In the case of polymorphic materials, we also find that the crystallization rate of various phases is differentiated by the rate of growth with respect to the collective variable, thus indicating a structural dependence. These results suggest that metadynamics can provide not only thermodynamic, but also mechanistic and kinetic, insight into complex crystallization phenomena.

Modeling crystallization pathways of polymorphic materials: Enhanced sampling techniques and method development

2019 Fall National Meeting

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