Multicomponent Crystallization Via Bottom-Up Coarse-Grained Modeling: CO2 Hydrate Formation

The formation of carbon dioxide (CO2) clathrate hydrates is critical for technologies ranging from carbon sequestration to cold energy applications. While all-atom simulations provide molecular insight, their computational cost severely limits the study of hydrate nucleation and growth. Coarse-grained (CG) models offer a compelling alternative for reaching the necessary time and length scales. In this work, we develop a novel CG model for the CO2-water system using a bottom-up approach. We utilize the BUMPer model, an effective pairwise potential that implicitly captures water's many-body effects, and systematically derive the remaining CO2-CO2 and water-CO2 interactions. Our central finding is that a single potential for the water-CO2 interaction cannot adequately describe both the disordered aqueous solution and the structured solid hydrate. To overcome this, we introduce a state-dependent approach, deriving separate potentials from prenucleation liquid and crystalline hydrate configurations. This composite potential, which is also pairwise, accurately captures the phase transition, successfully driving the formation of stable hydrate crystals and promoting the self-assembly of individual cages. This work establishes that complex multicomponent crystallization can be modeled using only two-body CG potentials, providing a robust and computationally efficient methodology for studying hydrate dynamics.