(582c) Quantifying Clathrate Hydrate Nucleation and Growth From Molecular Simulations

Despite their industrial significance and ubiquity, the formation mechanism of hydrates remains poorly understood.  The challenges associated with describing hydrate nucleation and growth mechanisms remain at the forefront of fields such as hydrogen storage, carbon dioxide sequestration, and hydrocarbon transportation and recovery.  Various mechanisms of hydrate formation have been postulated, most involving the annealing of an amorphous or partially-ordered aggregation of cages into the thermodynamically-preferred crystal structures. In this talk, we will present an overview of our efforts in understanding clathrate hydrate nucleation and growth using molecular simulations, including defining the thermodynamics phase space and direct simulations capturing the different stages through the nucleation and growth processes. The molecular events during nucleation and growth are quantified by applying different order parameters to represent the structuring of water and gas molecules. One of the approaches is based on a Voronoi tessellation analysis, which provides information on the cooperative ordering of gas and water molecules. In applying the tessellation to the nucleating trajectories, we observe that several of the Voronoi properties (polyhedra volume, total surface area, asphericity parameter) show strong signatures of change when hydrates nucleate. The results suggest that the Voronoi tessellation analysis is a powerful and efficient tool that can be applied to obtain further insight into the mechanisms associated with the ordering of methane and water molecules in the nucleation and growth processes of hydrates.