Reaction Coordinate of Incipient Methane Clathrate Hydrate Nucleation

Gregg Beckham, Brandon Knott, Brian Barnes, David Wu, Amadeu Sum

Research output: Contribution to journalArticlepeer-review

83 Scopus Citations

Abstract

Nucleation from solution is a ubiquitous phenomenon with relevance to myriad scientific disciplines, including pharmaceuticals, biomineralization, and disease. One prominent example is the nucleation of clathrate hydrates, multicomponent crystalline inclusion compounds relevant to the energy industry where they block pipelines and also constitute a potential vast energy resource. Despite their importance, the molecular mechanism of incipient hydrate formation remains unknown. Herein, we employ advanced molecular simulation tools (pB histogram, equilibrium path sampling) to provide a statistical-mechanical basis for extracting physical insight into the molecular steps by which clathrates form. Through testing the Mutually Coordinated Guest (MCG) order parameter, we demonstrate that both guest (methane) and host (water) structuring are crucial to accurately describe the nucleation of hydrates and determine a critical nucleus size of MCG-1 = 16 at 255 K and 500 bar. Equipped with a validated (and novel) reaction coordinate, subsequent equilibrium path sampling simulations yield the free energy barrier and nucleation rate. The resulting quantitative nucleation process is described by the MCG clustering mechanism. This constitutes a significant advance in the field of hydrates research, as the fitness of a molecular descriptor has never been statistically verified. More broadly, this work has significance to a wide range of multicomponent nucleation contexts wherein the formation mechanism depends on contributions from both solute and solvent. (Graph Presented).

Original languageAmerican English
Pages (from-to)13236-13243
Number of pages8
JournalJournal of Physical Chemistry B
Volume118
Issue number46
DOIs
StatePublished - 20 Nov 2014

Bibliographical note

Publisher Copyright:
© 2014 American Chemical Society.

NREL Publication Number

  • NREL/JA-5100-63630

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