How crystals form: a theory of nucleation pathways.

Classical Density Functional theory is combined with fluctuating hydrodynamics to describe nucleation in general and crystallization in particular. The nucleation pathway is characterized as the most likely path connecting the initial homogeneous solution to the critical cluster[1]. Classical Nucleation Theory can be recovered with additional approximations[2]. Results for a Lennard-Jones system[3] show a two-step path with the formation of a dense fluid-like droplet followed by the development of order within. During ordering, the system passes through a metastable, subcritical phase that could be identified as a nucleation precursor. The precuror is a sub-critical crystalline cluster stabilized by completed crystalline shells and a wetting layer.

[1] J. F. Lutsko, "A dynamical theory of nucleation for colloids and macromolecules", J. Chem. Phys. 136, 34509 (2012)
[2] J. F. Lutsko, "Systematically extending classical nucleation theory", New J. Phys. 20, 103015 (2018)
[3] J. F. Lutsko, "How crystals form: A theory of nucleation pathways", Science Adv., 5, eaav7399 (2019).