Methane-Hydrate Nucleation in Marine Environments: Insights from Molecular-Dynamics Strategies Exploring Free-Energy Landscapes

Molecular-dynamics simulations of methane hydrates in contact with silica surfaces have been performed, mimicking the marine environment. A set of suitable collective variables was employed to accelerate the exploration of the underlying free-energy landscape within the metadynamics approach. A set of conditional ensembles were collected along reactive paths. The conditional probability distribution function (PDF) of several order parameters was studied for each target system. We will discuss the mechanisms of methane-hydrate nucleation in the heterogeneous environment of silica surfaces and compare these to the homogeneous environment, providing useful insights on nucleation phenomena in both homogeneous and marine environments. This is helpful in the context of elucidating hydrate-nucleation phenomena with a view to potential exploitation of marine-hydrate gas resources.