Molecular dynamics simulation for surface melting and self-preservation effect of methane hydrate

• 来源期刊: 中国科学B辑（英文版）
• 年，卷（期）: 2008,（7）
• 页码范围: 651-660
• 页数: 10页
• 语种: 英文
• DOI: 10.1007/s11426-008-0016-5

摘要

The surface melting process of structure sl methane hydrate is simulated at T= 240, 260, 280, and 300 K using NVT molecular dynamics method. The simulation results show that a quasi-liquid layer will be formed during the melting process. The density distribution, translation, orientation, and dynamic properties of water molecules in the quasi-liquid layer are calculated as a function of the distance normal to the interface, which indicates the performance of quasi-liquid layer exhibits a continuous change from crystal-like to liquid-like. The quasi-liquid layer plays as a resistance of mass transfer restraining the diffusion of water and methane molecules during the melting process. The resistance of quasi-liquid layer will restrain methane molecules diffuse from hydrate phase to gas phase and slow the melting process, which can be considered as a possible mechanism of self-preservation effect. The performance of quasi-liquid layer is more crystal-like when the temperature is lower than the melt-ing-point of water, which will exhibit an obvious self-preservation. The self-preservation will weaken while the temperature is higher than the melting-point of water because of the liquid-like performance of the quasi-liquid layer.