Structure and stability of an amorphous water-methane mixture produced by cold compression of methane hydrate

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DOIResolve DOI: http://doi.org/10.1103/PhysRevB.86.054110
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TypeArticle
Journal titlePhysical Review B - Condensed Matter and Materials Physics
ISSN1098-0121
Volume86
Issue5
Article number54110
AbstractIn a process similar to the formation of high-density amorphous ice, amorphous methane hydrate was formed by the pressure-induced collapse of crystalline methane clathrate at 32 kbar and 100 K. This produced a regular array of methane embedded within cavities in an amorphous water network. In situ annealing results in further densification into a more disordered and higher density amorphous state before crystallization into ice VIII and hexagonal clathrate. Whereas the very high-density amorphous form of pure water undergoes a glass transition near 130 K at low pressure and crystallizes over a broad pressure range at ∼160 K, the amorphous network of the water-methane binary system exhibits a region of metastability that persists up to 220 K between 15 and 40kbar. It appears that in this system the connectivity of the water network exhibits sufficiently low mobility so as to inhibit the diffusion and phase separation of the constituents until 220 K, where the high-pressure ice VIII crystallization can occur. The structure of the amorphous form is studied by neutron diffraction and the hydration of methane in this disordered water network is more closely related to the small clathrate cage than the large. ©2012 American Physical Society.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); NRC Steacie Institute for Molecular Sciences (SIMS-ISSM)
Peer reviewedYes
NPARC number21269261
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Record identifier34bbba1f-1f61-4c2d-9432-4909084e2f5a
Record created2013-12-12
Record modified2016-05-09
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