Diffusion Enhances Chirality Selection

TL;DR

This study uses Monte Carlo simulations to show that diffusion enhances chirality selection in a reaction-diffusion system, lowering the critical concentration needed for chiral symmetry breaking and bridging diffusionless and homogeneous limits.

Contribution

It demonstrates how diffusion influences chirality selection and provides an interpolation formula connecting different diffusion regimes in a reaction-diffusion model.

Findings

Diffusion lowers the critical concentration for chiral symmetry breaking.

Chiral order decreases with dilution below a critical concentration.

The relation between enantiomeric excess and concentration fits an interpolation formula.

Abstract

Diffusion effect on chirality selection in a two-dimensional reaction-diffusion model is studied by the Monte Carlo simulation. The model consists of achiral reactants A which turn into either of the chiral products, R or S, in a solvent of chemically inactive vacancies V. The reaction contains the nonlinear autocatalysis as well as recycling process, and the chiral symmetry breaking is monitored by an enantiomeric excess $\phi$. Without dilution a strong nonlinear autocatalysis ensures chiral symmetry breaking. By dilution, the chiral order $\phi$ decreases, and the racemic state is recovered below the critical concentration $c_c$. Diffusion effectively enhances the concentration of chiral species, and $c_c$ decreases as the diffusion coefficient $D$ increases. The relation between $\phi$ and $c$ for a system with a finite $D$ fits rather well to an interpolation formula between the diffusionless(D=0) and homogeneous ($D=\infty$) limits.