Effect of coarse graining in water models for the study of kinetics and mechanisms of clathrate hydrates nucleation and growth.

This article focuses on comparing the effects of coarse-graining in water models on the nucleation and growth of methane clathrate hydrates, specifically contrasting the coarse-grained mW model with the all-atom TIP4P force field. Using dynamical nonequilibrium molecular dynamics simulations, the study finds that while both models yield similar thermodynamic properties such as critical nucleus size and free energy curvature, their dynamical properties differ by orders of magnitude, with mW exhibiting significantly faster nucleation and growth kinetics. This difference is attributed to the absence of explicit hydrogen atoms in the mW model, which accelerates water reordering necessary for clathrate cage formation, a process slower in TIP4P due to hydrogen-bond orientation dynamics. Additionally, both models produce nuclei containing a mixture of stable structure I and less stable structure II phases, with the TIP4P model showing a stronger dependence of cage composition on methane concentration. These findings highlight the impact of water model resolution on the kinetics and structural characteristics of methane clathrate crystallization.