Nucleation of methane hydrates at moderate subcooling by molecular dynamics simulations

Felipe Jiménez-Ángeles, Abbas Firoozabadi*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

86 Scopus citations

Abstract

Methane hydrates are crystalline structures composed of cages of hydrogen-bonded water molecules in which methane molecules are trapped. The nucleation mechanisms of crystallization are not fully resolved, as they cannot be accessed experimentally. For methane hydrates most of the reported simulations on the phenomena capture some of the basic elements of the full structure. In few reports, formation of crystalline structures is reached by imposing very high pressure, or dynamic changes of temperature, or a pre-existing hydrate structure. In a series of nanoscale molecular dynamics simulations of supersaturated water-methane mixtures, we find that the order of the crystalline structure increases by decreasing subcooling. Crystalline structures I and II form and coexist at moderate temperatures. Crystallization initiates from the spontaneous formation of an amorphous cluster wherein structures I, II, and other ordered defects emerge. We observe the transient coexistence of sI and sII in agreement with experiments. Our simulations are carried out at high methane supersaturation. This condition dramatically reduces the nucleation time and allows simulating nucleation at moderate subcooling. Moderate temperatures drive hydrates to more ordered structures.

Original languageEnglish (US)
Pages (from-to)11310-11318
Number of pages9
JournalJournal of Physical Chemistry C
Volume118
Issue number21
DOIs
StatePublished - May 29 2014
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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