From Nonclassical to Classical: Crystallization Seeds Reshape Nucleation Mechanisms.

Area of Science:

• Materials Science
• Chemical Engineering
• Crystallography

Background:

• Crystalline seeds accelerate nucleation and control polymorphs, but their effect on nucleation mechanisms is unclear.
• Homogeneous nucleation often involves nonclassical pathways with amorphous intermediates, yet seeds promote heterogeneous nucleation.

Purpose of the Study:

• To investigate how crystalline seeds alter nucleation mechanisms and polymorph selection.
• To provide direct evidence of seeds influencing classical versus nonclassical crystallization pathways.

Main Methods:

• Molecular dynamics simulations of zeolite synthesis.
• Analysis of competing nucleation processes and intermediate interfacial polymorphs.

Main Results:

• Crystalline seeds bypass amorphous intermediates, shifting nonclassical to classical, monomer-by-monomer crystallization.
• Nucleation outcomes depend on the thermodynamic stability and kinetic favorability of interfacial polymorphs.
• Synthesis environment (monomers vs. aggregates) and supersaturation level dictate pathway dominance, even with seeds.

Conclusions:

• Seeds offer a general framework for controlling crystallization mechanisms, kinetics, and polymorph selection.
• Findings have broad implications for materials science, pharmaceuticals, biominerals, and catalysis.
• This work provides a basis for engineering crystallization in diverse applications.