title: Secondary Crystal Nucleation: Nuclei Breeding Factory Uncovered.
abstract: Secondary nucleation, wherein crystal seeds are used to induce crystallization, is widely employed in industrial crystallizations. Despite its significance, our understanding of the process, particularly at the molecular level, remains rudimentary. An outstanding question is why do a few seeds give rise to a many-fold increase in new crystals? Using molecular simulation coupled with experiments we have uncovered the molecular processes that give rise to this autocatalytic behavior. The simulations reveal formation of molecular aggregates in solution, which on coming in contact with the surface of the seed undergo nucleation to form new crystallites. These crystallites are weakly bound to the crystal surface and can be readily sheared by fluid, making the seed surfaces available again to repeat the process. Further, the new crystallites on development can in turn serve as seeds. This mechanistic insight will enable better control in engineering crystalline products to design.
authors: Chemical Theory and Computation, Department of Chemistry, Lancaster University, Lancaster LA1 4YB (UK). j.anwar@lancaster.ac.uk.
authors: Jamshed
authors: J
authors: Anwar
authors: Department of Pharmacy, University of Malakand, KPK (Pakistan).
authors: Shahzeb
authors: S
authors: Khan
authors: Pharmaceutical Development, AstraZeneca R&D Mölndal, 43183 Mölndal (Sweden).
authors: Lennart
authors: L
authors: Lindfors
keywords: classical nucleation theory; crystal seeding; crystallization; molecular dynamics simulation; secondary nucleation