Molecular Insights into the Homogeneous Melting of Methane Hydrates

Although the melting of gas hydrates tends to be heterogeneous in most cases, in principle, this process can also be homogeneous when surface melting is properly inhibited. In this work, we investigated the molecular mechanisms of the homogeneous melting of superheated methane hydrates by means of molecular dynamics simulations. The homogeneous melting processes were found to be stochastic with varied induction times. We observed the formation of structural defects within the hydrogen-bonded water lattices of hydrate crystals during the induction times. The methane molecules were found to be relatively more stable within the gas hydrate phases, which might be responsible for the high stability of the superheated metastable methane hydrates. Although the melting processes involve the collective motion of water and methane molecules, the current work suggests that the migration and aggregation of methane molecules are critical in initiating the homogeneous melting of gas hydrate crystals.