Molecular dynamics characterization of the interfacial structure and forces of the methane-ethane sII gas hydrate interface

The nucleation of gas hydrates is of great interest in flow assurance, global energy demand, and carbon capture and storage. A complex molecular understanding is critical to control hydrate nucleation and growth in potential applications. Molecular dynamics is employed combined with the mechanical definition of surface tension to assess the surface stresses controlling interfacial behavior. We characterize the interfacial tension for sII methane/ethane hydrate and gas mixtures for different temperatures and pressures. We find that the surface tension trends positively with temperature in a balance of water-solid and water-gas interactions. The molecular dipole shows the complexities of water molecule behavior in small, compressed pre-melting layer that emerges as a quasi-liquid. These behaviors contribute to the developing knowledge base surrounding practical applications of this interface. • Configuration analysis solidifies equilibrium measures in molecular dynamics. • Gas molecules accumulate on the surface of the pre-melting layer. • Water displays multidimensional alignment in the pre-melting layer of gas hydrate. • Water aligns parallel to the surface of highest probability of hydrogen bonding.