In this paper we will discuss the first successful molecular simulation studies exploring the statesteady
crystal growth of sI and sII methane hydrates. Since the molecular modeling of the crystal
growth of gas hydrates has proven in the past to be very challenging, we will provide a brief
overview of the simulation framework we have utilized to achieve heterogeneous growth within
timescales accessible to simulation. We will probe key issues concerning the nature of the
solid/liquid interface for a variety of methane hydrate systems and will make important
comparisons between various properties. For example, the interface demonstrates a strong affinity
for methane molecules and we find a strong tendency for water molecules to organize into cages
around methane at the growing interface. The dynamical nature of the interface and its
microfaceted features will be shown to be crucial in the characterization of the interface. In
addition to the small and large cages characteristic of sI and sII hydrates, water cages with a 51263
arrangement were identified during the heterogeneous growth of both sI and sII methane hydrate
and their potential role in cross-nucleation of methane hydrate structures will be discussed. We
will describe a previously unidentified structure of methane hydrates, designate structure sK,
consisting of only 51263 and 512 cages, and will also show that a polycrystalline hydrate structure
consisting of sequences of sI, sII and sK elements can be obtained. In this paper we will also
detail a variety of host defects observed within the grown crystals. These defects include vacant
cages, multiple methane molecules trapped in large cages, as well as one or more water molecules
trapped in small and large cages. Finally, preliminary results obtains for THF and CO2 hydrates
will be presented and their behaviour contrasted to that of methane hydrate.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/1164 |
| Date | 07 1900 |
| Creators | Kusalik, Peter G., Vatamanu, Jenel |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Rights | Kusalik, Peter G. |
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