Stability and Composition of Helium Hydrates Based on Ices Ih and II at Low Temperatures

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• 作者：Rodion V. Belosludov ; Yulia Y. Bozhko ; Oleg S. Subbotin ; Vladimir R. Belosludov ; Hiroshi Mizuseki ; Yoshiyuki Kawazoe ; Vasily M. Fomin
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：February 6, 2014
• 年：2014
• 卷：118
• 期：5
• 页码：2587-2593
• 全文大小：386K
• ISSN：1932-7455

文摘

The recently developed approach describing host lattice relaxation, guest鈥揼uest interactions and the quantum nature of guest behavior (Belosudov, R. V.; Subbotin, O. S.; Mizuseki, H.; Kawazoe, Y.; Belosludov, V. R. J. Chem. Phys. 2009, 131, 244510) has been used to derive the thermodynamic properties of helium hydrates based on ices I_h and II. The p鈥?i>T phase diagrams of the helium hydrates in different ices are presented for a wide range of pressures and temperatures, and the structural transitions between pure ice I_h and ice II as well as between ice I_h-based helium hydrate and ice II-based helium hydrate have been found to be in agreement with the available experimental data. The 鈥渋ce II-based helium hydrate鈥搃ce I_h-based helium hydrate鈥?equilibrium shifts toward the higher pressures in comparison with the line of 鈥渋ce II鈥搃ce I_h鈥?equilibrium. The degrees of interstitial space filling by helium in ice I_h-based and ice II-based hydrates decrease with increasing temperature and lowering of pressure. It is demonstrated that the helium filling in ice I_h proceeds more slowly than in ice II. However, the mole fraction of helium in the hydrate based on ice I_h is significantly higher than that in the ice II-based hydrate. We predict that during the phase transition from the ice I_h-based hydrate to the ice II-based one a discharge of gaseous helium should be observed. This may serve as an indicator of the phase transition in experiment.