Mechanical instability of monocrystalline and polycrystalline methane hydrates
Wu, Jianyang; Ning, Fulong; Trinh, Thuat; Kjelstrup, Signe; Vlugt, Thijs J.H.; He, Jianying; Skallerud, Bjørn Helge; Zhang, Zhiliang
Journal article, Peer reviewed
Åpne
Permanent lenke
http://hdl.handle.net/11250/2384189Utgivelsesdato
2015Metadata
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- Institutt for kjemi [1404]
- Institutt for konstruksjonsteknikk [2483]
- Publikasjoner fra CRIStin - NTNU [38680]
Sammendrag
Despite observations of massive methane release and geohazards associated with gas
hydrate instability in nature, as well as ductile flow accompanying hydrate dissociation in
artificial polycrystalline methane hydrates in the laboratory, the destabilising mechanisms of
gas hydrates under deformation and their grain-boundary structures have not yet been
elucidated at the molecular level. Here we report direct molecular dynamics simulations of
the material instability of monocrystalline and polycrystalline methane hydrates under
mechanical loading. The results show dislocation-free brittle failure in monocrystalline
hydrates and an unexpected crossover from strengthening to weakening in polycrystals. Upon
uniaxial depressurisation, strain-induced hydrate dissociation accompanied by grain-boundary
decohesion and sliding destabilises the polycrystals. In contrast, upon compression,
appreciable solid-state structural transformation dominates the response. These findings
provide molecular insight not only into the metastable structures of grain boundaries, but also
into unusual ductile flow with hydrate dissociation as observed during macroscopic
compression experiments.