How to Identify the Crystal Growth Unit

The structure and composition of the crystal growth unit are huge fundamental practical consequence. We propose a method to identify solute species that incorporates into site on surfaces, kinks, which rests kinetics elementary reaction at kinks. use as model crystals olanzapine, an antipsychotic medication, etioporphyrin I, field-effect transistor. combine time-resolved in situ atomic force microscopy with Raman absorption spectroscopies, complemented by density functional theory all-atom molecular dynamics modeling solutions. show cannot be deduced neither from oligomers nor structure. Chemical analyses reveal if dominant is one sites, then layer complies monomolecular rate law. By contrast, assembles two units form, bimolecular law ensues. Solutions both olanzapine I dominated monomers, exist equilibrium minority dimers. Whereas numerous structures incorporate dimer motifs, organize stacks monomers. Olanzapine grow incorporation One studied face grows majority whereas other selects dimers unit. results highlight power crystallization illuminate most challenging issues growth.