Competing Dipole Ordering and Hydrogen-Bond Reorganization Regulate Hydrogen-Tetrahydrofuran Clathrate Growth at the Hydrate–Liquid Interface

Abstract

Electric fields reorganize interfacial water and can therefore alter clathrate hydrate growth, but the molecular origin of the frequently nonmonotonic response remains unresolved. Here, molecular dynamics simulations are used to examine seeded hydrogen-tetrahydrofuran (H2-THF) structure-II hydrate growth in a gas–liquid-hydrate system at 270 K and 40 MPa under fields of 0–0.6 V/nm. Among the sampled conditions, 0.4 V/nm produces the largest cage-growth rate and H2 incorporation, whereas fields of 0–0.2 V/nm have modest effects and 0.3 V/nm shows pronounced trajectory dependence. Stronger fields initially accelerate cage formation but subsequently promote stagnation or cage loss. The nonmonotonic response arises from a coupled multiscale mechanism linking field-induced dipole ordering, interfacial hydrogen-bond dynamics, and cage-topology evolution. Specifically, moderate fields (0.4 V/nm) induce weak dipole preorganization that extends the interfacial hydrogen-bond lifetime by approximately 18%, which in turn minimizes anomalous cage transformations while maximizing transformation pathway diversity, thereby coupling molecular orientation through hydrogen-bond persistence to efficient and sustained cage-network propagation. In contrast, strong fields (≥0.5 V/nm) impose coercive dipole alignment that suppresses hydrogen-bond exchange, contracts the cage-transformation network to a restricted set of reversibly interconverting cage pairs, and destabilizes long-range lattice propagation. These results show that maximum clathrate growth does not coincide with maximum molecular alignment. Instead, an intermediate field creates an adaptable interfacial hydrogen-bond network that couples water orientation, cage topology, and guest incorporation.