Molecular Dynamics Study of Facet Dependence and Kinetic Regulation of Methane Hydrate Growth.

Gas hydrate formation poses critical flow assurance challenges in natural gas production and transportation systems, yet the facet-dependent growth kinetics of hydrates and its modulation by external agents remain poorly understood. In this work, molecular dynamics simulations were employed to systematically investigate methane hydrate growth on different crystal facets and to elucidate the corresponding kinetic regulation under varying spatial distributions of kinetic hydrate inhibitors (KHIs). The results demonstrate pronounced facet-dependent growth kinetics, with growth rates following the order (100) > (110) > (111), governed by differences in methane transport pathways and interfacial structural constraints. A transition from transport-dominated to interfacial assembly controlled growth is suggested across crystal facets, revealing the important roles of methane enrichment and water structuring at the interface. Furthermore, kinetic regulation exhibits strong facet and location dependence. KHIs at the gas-liquid interface primarily regulate methane transport and interfacial water organization, whereas those near the hydrate surface appear to directly disrupt the cooperative assembly of methane and water molecules, resulting in enhanced inhibition efficiency, particularly on the (111) facet. These findings establish a mechanistic link between hydrate growth behavior and inhibitor action, providing molecular-level insights into facet-dependent hydrate formation and its kinetic regulation.