Formation and Decomposition Mechanisms for Clathrate Hydrates

Large-scale nanosecond classical molecular dynamics calculations have been employed to simulate initial clathrate hydrate formation. Preferential formation of small (5¹²) cages in the initial stages of clathrate formation is not found. This observation is compared to the recent NMR observations on the formation of small cages preceding the crystallization process. The result seems to support experimental observations that the formation of structure II SF₆ hydrate does not require occupation of small cages. The decomposition mechanism of gas hydrates has been investigated using classical molecular dynamics. The ‘preservation effect’ that inhibits decomposition of gas hydrates at temperatures above its thermodynamic melting or decomposition points may be explained with a phenomenological model assuming the formation of a thin ice crust layer.