Visualization of Molecular Dynamics by Simulation

Abstract

The mechanism of formation of methane hydrate is investigated here at a molecular level. The key to whether or not methane hydrates can be formed is the stability of the hydrate structure. This paper deals with a computer simulation of methane hydrate type 1 formation by a molecular dynamics method and an accurate description of the crystal structure. Computer simulation results show that very stable type 1 methane hydrates can be formed below 275 K, in which 46 water and 8 methane molecules are contained in a single cubic unit cell of length 12.0 A. Above 275 K, the stability of the hydrates increasingly degrades, logarithmically as a power function, up to 300 K, with no stability at 350 K. Pressure, as a parameter of formation conditions, increases with temperature and becomes tremendously high at 350 K. Hydrates with various hydration numbers (at least one guest molecule in a small cage) have roughly the same degree of stability, but higher pressures are required for hydrates with fewer guest molecules. Empty hydrates dissolve above 275 K.