Structural Transition and Tuning of tert-Butylamine HydrateThis research was performed by the National Research Laboratory (NRL) Program of KOSEF funded by the Ministry of Science and Technology of Korea, and also partially supported by the Brain Korea 21 Project

Gas hydrates, or more generally clathrate hydrates, are a type of inclusion compound and take the form of nonstoichiometic solid crystalline materials formed from water and small guest molecules. Under sufficient pressure of the guest material and at specific temperatures, 3D hydrate structures are formed by the stacking of polyhedral cages of hydrogenbonded water molecules. Suitably sized guest molecules are enclathrated in cages and their presence stabilizes the compounds formed. Although the guest molecules are physically enclosed within the cages, there are no direct chemical bonds between host water molecules and guest molecules. In general gas hydrates form three distinct structural families known as structure I (sI), structure II (sII), and structure H (sH), which differ in the combination of cage types required to build a 3D structure. In addition, there are a variety of more complex clathrate hydrate structures, labeled as types III–VII and structure T (sT). It is clear that many of the physical attributes of gas hydrates remain unknown and thus need to be examined in more detail. The gas hydrates are of particular interest in the fields of energy research and environmental science because of the possible applications for the storage of natural gas, sequestration of CO2 in the deep ocean, [5] and separation of greenhouse gases from flue gas. It is noteworthy that for lowering the pressure of hydrate formation without significant reduction of the capacity to store CH4, the use of sH hydrate was suggested. [7]