Computer Simulation for the Formation and Stability of Methane Hydrate Nanostructure

Molecular dynamics (MD) simulation is performed to obtain the formation mechanism and stability of methane clathrate hydrate nanostructure. Gas hydrate nucleation and cage formation is an important step to understand hydrate formation phenomenon. It is demonstrated that the water molecules formed the characteristic cage structure of type I clathrate hydrate around the methane guest molecules after 1 ns by reducing the temperature from 400 to 275 K in the NVT ensemble condition. The simple point charge (SPC) potential model is used for water-water molecules interactions and Lennard-Jones potential for guest-guest and host-guest interactions. Formation of methane hydrate structure is described based on the interactions between guest-host molecular forces and cage structure configuration. Then, the stability of methane clathrate hydrate structure is studied during the simulation time of 200 ps. In order to evaluate the structure of clathrate hydrate, the radial distribution functions (RDFs) of host-host, host-guest and guestguest molecules are obtained. Also, the time variation of kinetic energy, potential energy and total energy demonstrate the studied system achieves to an equilibrium state. The obtained results show that the methane molecules interactions on the water host lattice cannot decompose its basic structure and therefore the presence of the methane guest molecules in the clathrate hydrate helps to more stability of clathrate hydrate structure.

کلیدواژه ها:

Methane hydrate ، Computer simulation ، Molecular dynamics ، Formation ، Stability