Molecular Modeling of Nucleation and Growth of Clathrate Hydrates

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Valeria Molinero of the University of Utah is supported by an award from the Chemical Structures, Dynamics and Methods program in the Chemistry Division for a computational study aimed at elucidating microscopic pathways by which clathrate hydrates nucleate and grow from aqueous solutions and from ice. The project combines the power of advanced simulation methods to sample rare nucleation events with atomistic and coarse-grained molecular dynamics simulations. The project tests a transformative hypothesis: that a monatomic model of water with very short-ranged interactions and without hydrogen atoms but able to form the characteristic tetrahedral ?hydrogen-bonded" configurations of water, produces nucleation and grow of clathrates following the same pathways than fully atomistic water models. If this method is validated, it will permit the study of molecular mechanisms at less than 1% of the computational cost. The study is the first to determine the molecular mechanisms of formation and structure of the nuclei for clathrates containing large guest and hydrophilic guests and two distinct guests (double clathrates). It is the first project to investigate the mechanisms of nucleation and growth of clathrates from ice and the structures of the ice/clathrate and ice/guest interfaces using simulations.Clathrate hydrates hold high promise as an abundant energy source, for storage and transportation of natural gas and hydrogen, and for sequestration of carbon dioxide. A prominent challenge for these applications is the slow kinetics of formation of gas hydrate clathrates. On the other hand, clathrate plugs form in oil and gas pipelines, causing enormous economic losses and safety concerns. A key impediment to retard or hasten the crystallization of clathrates is the lack of understanding of the molecular mechanisms by which they nucleate and grow. A professor from Westminster College, an undergraduate institution, is participating in this project, as well as undergraduates and graduate students. The PI and her research group also participate in an outreach program to high schools called "The Leo on Wheels" of the Utah Science Center.