Molecular Dynamics Studies On The Structure And Stability Of Carbon Dioxide Hydrate

Sub-sea sediments sequestration of carbon dioxide hydrate is considered as an effective method to mitigate global warming.To prevent hydrate decomposition by external factors is the key to commercial application,the leakage of carbon dioxide will cause secondary pollution and change the ecological environment.Therefore,ensuring the continuance and stabilization of hydrate sealed is an important research project.This paper is to consider the influence of the water molecular force field,temperature and pressure factors on the hydrate structure and stability,and to provide a reference for choosing geological regional effectively by obtaining a stability zone,avoiding hydrate decomposition because of the high temperature.From the perspective of the field of gas hydrate research,scholars have more research and made great progress for hydrate structure,phase equilibrium problems,generation and decomposition dynamics theory and so on.Predecessors in terms of carbon dioxide hydrate stability use the same kind of water molecular force field to research hydrate stability in different temperature or time period.In this paper,we study the influence of six different water molecular force field(SPC,SPC/E,TIP4 P,TIP4P-Ew,TIP4P/2005,TIP4P/Ice)on the structure and stability of hydrate.Simulation results show that different force fields have good precision and consistency to hydrate crystal cell length,hydrogen bond length and the average length of the hydrogen bond.But there is a big difference on the stability of gas hydrates,through the comparison with the experimental value,choosing SPC force field of small errors are further simulated hydrate structure stability increasing with pressure.The anslysis of molecular dynamics simulation indicate that the higher the deep sea,the more favorable of hydrate storage.Through hydrate trajectory files at 5 MPa,to understand the microscopic details of hydrate structure in the process of instability.At last,simulation obtain the critical value of hydrate solid and liquid phase,and hydrate stability zone in the depths of 1000 m under simplified conditions.