Transient Translational and Rotational Water Defects in Gas Hydrates

• Main Authors: Liang, Shuai, Liang, Deqing, Wu, Nengyou, Yi, Lizhi, Hu, Gaowei
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: Science & Technology; Physical Sciences; Technology; Chemistry; Science & Technology - Other Topics; Materials Science; TETRAHYDROFURAN CLATHRATE HYDRATE; MOLECULAR-DYNAMICS SIMULATIONS; HETEROGENEOUS CRYSTAL-GROWTH; METHANE HYDRATE; CARBON-DIOXIDE; ICE; HYDROGEN; CO2; NUCLEATION; MECHANISM; Physical; Nanoscience & Nanotechnology; Multidisciplinary; Methane hydrate
• Online Access: http://ir.giec.ac.cn/handle/344007/15763

We report our observations of the transient formation of the translational and rotational defects in the host lattice of methane hydrates. We perfortn molecular dynamics simulations of a fully occupied methane hydrate system and find that the hydrogen bonds of a water molecule can be thermally broken, and the water molecule can: then rotate more freely. We observe the formation of transient Bjerrum defects around, the water: molecule, and the two hydrogens of the water molecule can be interchanged when the transient defects anneal. The 95% confidence interval for the rate of the hydrogen interchange is estimated to be 1.3 X 10(5)-2.4 X 10(5) s(-1) per water molecule, and the 95% confidence interval for the associated free energy of activation is estimated to be 38.2-39.4 kJ/mol at 270 K. We also observe the transient formation of vacancy-interstitial water defects. The, formation and annealing of these vacancy-interstitial defects can result in the interchange of two or three neighboring water molecules on the gas hydrate lattices. The 95% confidence interval for the rate of the formation of transient vacaney-interstitial water defects as a result of the water interchanges is estimated to be 6.7 x 10(2)-1.6 X 10(4) s(-1) per water molecule and. the 95% confidence interval for the associated free energy of activation is estimated to be 44.1-51.3 kJ/mol at 270 K.