The elementary reactions for incorporation into crystals

Area of Science:

• Physical Chemistry
• Materials Science
• Crystallization Dynamics

Background:

• Crystal growth rates depend on solute-kink reactions, but the bond-breaking and rebuilding process is poorly understood.
• Elucidating the molecular mechanisms at crystal growth sites is essential for controlling crystallization.

Purpose of the Study:

• To investigate the microscopic structures and dynamics of solute molecules reacting with crystal kinks.
• To understand the elementary steps involved in solute incorporation into crystal kinks.

Main Methods:

• Utilized four solvents with distinct functionalities to probe reaction pathways.
• Combined time-resolved in situ atomic force microscopy, X-ray, optical methods, and molecular dynamics simulations.

Main Results:

• Solute molecules (etioporphyrin I) directly reach crystal steps from solution.
• Solute binding to kinks occurs in two steps: partial desolvation and attachment, followed by bond breaking and relocation.
• Preliminary bond strength to the kink dictates the incorporation energy barrier.

Conclusions:

• Identified the rate-limiting step in crystal growth as the solute-kink reaction.
• Demonstrated the existence of an intermediate state whose stability is solvent-dependent.
• This understanding can guide the development of solutions to control crystallization processes in industry and nature.