How Crystal Size and Number Steer Asymmetric Crystallization.

Chiral amplification processes during crystallization can hinge on subtle asymmetries in crystal populations, yet the underlying kinetic drivers remain elusive. Here we experimentally investigate how size and mass imbalances between two enantiomeric crystal populations translate to asymmetric growth rates that determine asymmetric crystal growth. We find that the interplay between imbalances in size and mass can yield positive, linear or even negative nonlinear chiral amplification. Consequently, though small crystals have a thermodynamically higher solubility than large ones, a minority population of small crystals can collectively outgrow and ultimately dominate a majority of larger crystals. This amplification due to size effects can be further enhanced or dampened by controlling growth rates. Our findings uncover an intricate kinetic selection mechanism driven by population-level growth rates and governed by fundamental crystallization dynamics. Together, these results provide new insights into the origin of nonlinear amplification phenomena and offer practical guidance for competitive asymmetric crystallization and self-assembly processes.