LAUSR

Abstract The stability of CH4, CO2, and H2S in four two-dimensional hydrates, denoted as 2D-I, 2D-II, 2D-III, and 2D-IV, was investigated by the first-principle calculations and molecular dynamics simulations. The result shows that two-dimensional CH4 hydrates are thermodynamically and dynamically stable. CO2 can only form the 2D-I and 2D-II hydrates, while these structures are dynamically unstable. Four two-dimensional H2S hydrates are thermodynamically stable, but only the 2D-I structure is dynamically stable. Further, simulation result suggests that the stability of the two-dimensional hydrate can be increased at low temperatures or in the confined environments (for example, nano-slits). As for the 2D-I binary hydrate, its thermodynamic stability is in between two corresponding pure hydrates, and only the CH4-H2S binary hydrate is dynamically stable. The CH4-CO2-H2S ternary hydrate is dynamically unstable because of the overflow of CO2.