Electric Field-Controlled Structural Instability and Mechanical Properties of Methane Hydrates

Gas hydrates play a significant role in the broad areas of energy applications and climate changes. Furthermore, externally applied fields by charged sediments and artificial activities are of paramount importance for transitions between disordered and ordered gas hydrate systems on the Earth. Herein, the role of external static electric fields in the structural instability and mechanical properties of methane hydrates are explored using molecular dynamics simulation methods. Our simulation results show that mechanical characteristics of methane hydrates such as Young's modulus, strengths, and failure modes are greatly affected by strengths and imposed directions of external electric fields. Interestingly, strong electric fields can result in the distortion and dissociation of local water cages in methane hydrates mainly due to realignments of water molecules, thereby weakening their mechanical properties. Moreover, instability failure modes of methane hydrates can be attributed to notable reorientations of water molecules and molecular diffusions of water and methane molecules in methane hydrates. This work provides new insights into mechanics of natural crystalline gas hydrates, which is also helpful for understanding the mechanical instability of charged sediment-host natural gas hydrates.