Temperature-Driven Structural Transition of Methane Hydrate: Decoding Static Structure Factor Feature Peaks

Abstract

The microstructure of methane hydrates determines their stability, and subtle changes in the microstructure under different conditions can significantly affect the gas release efficiency during the extraction process or cause safety risks. Therefore, it is crucial to explore the microstructural changes at different temperatures for their exploitation and utilization. In this study, the structural changes of type I methane hydrate at different temperatures in the temperature interval of 210–290 K were investigated by molecular dynamics (MD) simulations combined with static structure factor (SSF), radial distribution function (RDF), and Lindemann index. It was found that the water molecules form a stable cage-like structure through an ordered hydrogen bonding network at 210 K. As the temperature rose to 290 K, the structural disorder was markedly enhanced, reflecting the disruption of ordered arrangements and the dominance of disordered molecular interactions. The structural changes of type I methane hydrate at different temperatures were investigated by the SSF, RDF, and Lindemann index. At low temperatures, different SSF peak positions (at q = 10–12.5, 17.5–22.5 and 30–35 nm^–1, respectively) corresponded to three environments around the central oxygen atom: tetrahedral coordination structure, pentagonal secondary structure, and cage-like host–guest structure, respectively. The present study reveals the correspondence between the structural changes and SSF of methane hydrates at different temperatures, which provides an important theoretical basis for the experimental study of the microstructure of methane hydrates and the development of efficient mining technology.