Decomposition dynamics of dodecahedron and tetrakaidecahedron structures in methane hydrate by molecular simulations

Abstract

The decomposition of dodecahedron and tetrakaidecahedron in methane hydrate is studied by molecular dynamics simulation. For each single cage‐like structure, the decomposition is divided into three stages according to the different characteristics in each stage. The interaction from each part of the system to the single cage‐like structure is analyzed. The feature of hydrogen bond and the transformation in vibration density of states of oxygen during decomposition are investigated. The influences of heat flow disturbance and different initial temperature are estimated. The results show that for two different size structures, the time required by each stage is different. However, the percentage of residual hydrogen bond basically keeps the same. When decomposing, the total interaction energy to the cage‐like structure increases and the vibration density of states of oxygen in cage‐like structure converts more similar to that in liquid water. It suggests that heat flow disturbances and higher initial temperature may exacerbate the decomposition of single cage‐like structure.

Pressure-Induced Stability of Methane Hydrate from Machine Learning Force Field Simulations

“…Figure c shows the snapshots of MHsI at various times at 565 K and 2 kbar. From these snapshots, we noticed that the decomposition of MHsI first experiences the destruction of water cages, and then the overflow and diffusion of methane molecules, which is consistent with previous MD simulation results using the classical force field. ,, …”

“…From these snapshots, we noticed that the decomposition of MHsI first experiences the destruction of water cages, and then the overflow and diffusion of methane molecules, which is consistent with previous MD simulation results using the classical force field. 21,25,27 To further illustrate the decomposition mechanism, we examine the evolution of D and T cages in MHsI, which were analyzed by the latest developed hierarchical topology ring algorithm. 48 As displayed in Figure 3, the evolution process of D and T cages is almost the same at 0, 2, and 4 kbar, respectively.…”

“…This technology has a certain research prospect in the simulation of hydrate phase behavior, nucleation and growth, , transport properties, , and chemical inhibition . However, there are few reports about the effect of pressure on the decomposition mechanism simulated by MD because its effect is not as significant as that of temperature, phase composition, and cage occupancy . English et al simulated the decomposition process of methane hydrate crystals surrounded by the liquid phase at 276.65 K and 68 bar .…”

Analysis of Influencing Factors and Kinetic Characteristics of Spherical Methane Hydrate Decomposition

“…Due to the absence of van der Waals forces between host and guest molecules, the crystal is extremely unstable. The decomposition process of the methane hydrate begins with the distortion and collapse of the cage structure on the crystal surface and is followed by the desorption of methane molecules from the hydrate surface . For the empty cage, no methane molecule diffuses from the interface to the liquid phase.…”

“…The decomposition process of the methane hydrate begins with the distortion and collapse of the cage structure on the crystal surface and is followed by the desorption of methane molecules from the hydrate surface. 42 For the empty cage, no methane molecule diffuses from the interface to the liquid phase. Thus, the mass transfer resistance is reduced.…”