AN ATOMISTIC LEVEL DESCRIPTION OF GUEST MOLECULE EFFECT ON THE FORMATION OF HYDRATE CRYSTAL NUCLEI BY AB INITIO CALCULATIONS
R.V. Belosludov1, H. Mizuseki1, M. Souissi1, Y. Kawazoe1, J. Kudoh2, O.S. Subbotin3, T.P. Adamova3, V.R. Belosludov3
1 Institute for Materials Research, Tohoku University
2 Center for Northeast Asia Studies, Tohoku University
3 Nikolaev Institute of Inorganic Chemistry Siberian Branch of Russian Academy of Sciences
subbot@niic.nsc.ru
Ключевые слова: methane, ozone, clathrate hydrate; nucleation mechanism; first-principles calculations
Страницы: 633-639
Аннотация
In the present study, we have reported the results of a systematic investigation of cage-like water structures using the first-principles calculations. These results show that, in the case of methane hydrate, the following nucleation mechanism can be revealed. The formation of small water cavities filled with methane is the first step of formation of methane hydrate. It is not necessary to occupy all dodecahedral cages by the guest molecules. After that the small cavities started to form the H-bonding network with surrounding water molecules and the small number of water molecules is enough for formation of stable hydrogen-bonding network. The structural information contained in such nuclei is conserved in the forming crystal. Moreover, it is also important the presence of methane molecule between small cages in order to prevent the adhesion of cavities. It has been found that the ozone molecule can also stabilize the small cage since the value of the interaction energy between the ozone guest and water host framework is very close to one obtained for methane case. However, ozone affects on the structure of large cavities and hence the second guest is necessary in order to stabilize the hydrate structure.
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