Chiral Crystal Growth under Grinding

TL;DR

This paper models chiral crystal growth under grinding, showing that combined autocatalytic effects and grinding-induced monomer recycling can rapidly lead to homochirality, unlike grinding or ripening alone.

Contribution

It introduces an extended lattice gas model incorporating autocatalytic chirality change and grinding effects to explain homochirality emergence.

Findings

Grinding alone cannot induce chirality selection.

Autocatalytic surface effects accelerate homochirality.

Recycling of monomers via grinding enables exponential enantiomeric excess growth.

Abstract

To study the establishment of homochirality observed in the crystal growth experiment of chiral molecules from a solution under grinding, we extend the lattice gas model of crystal growth as follows. A lattice site can be occupied by a chiral molecule in R or S form, or can be empty. Molecules form homoclusters by nearest neighbor bonds. They change their chirality if they are isolated monomers in the solution. Grinding is incorporated by cutting and shafling the system randomly. It is shown that Ostwald ripening without grinding is extremely slow to select chirality, if possible. Grinding alone also cannot achieve chirality selection. For the accomplishment of homochirality, we need an enhanced chirality change on crystalline surface. With this "autocatalytic effect" and the recycling of monomers due to rinding, an exponential increase of crystal enantiomeric excess to homochiral state is realized.