Ultra-Coarse-Grained Modeling of Chiral Molecular Fluids

Molecular chirality is ubiquitous in nature, and homochirality is a signature of life. Understanding molecular chiral symmetry breaking has critical applications in pharmaceuticals, catalysis, functional soft materials, and biomolecular assemblies. Molecular dynamics simulations can provide insights into the microscopic mechanisms of chiral symmetry breaking, but simulations of complex molecular chiral systems at atomistic resolution remain computationally prohibitive because chirality-driven phase behavior can occur over large length and time scales. To address this challenge, we develop a bottom-up ultra-coarse-grained (UCG) model of a chiral fluid in which each molecule is represented by a single UCG bead endowed with a binary probabilistic internal state representing molecular handedness. The dynamical evolution of the internal state is coupled to the configurational environment and modulates the coarse-grained interaction potential. This coupled evolution of the internal states and coarse-grained configurational dynamics permits the use of a highly coarsened single-bead representation of chiral molecules that would not be possible by conventional coarse-graining approaches. We show that the resulting UCG model can accurately simulate both the temperature- and density-dependent spontaneous chiral symmetry breaking from a racemic fluid into an enantiomerically rich phase. Our results demonstrate that the UCG framework provides an effective route for developing coarse-grained models to study chiral molecular fluids.