EMD simulation for potential and force at liquid-vapor interface system composed of water molecules

The interaction of potentials between molecules is important for the molecular interface behavior. The liquid-vapor interface system composed of water molecules is simulated and studied with equilibrium molecular dynamics (EMD) simulation method in this paper. The results agree with the known conclusions that there is a marked fall of potential between the liquid bulk and the vapor bulk. It is also indicated that different types of forces have different effects on the molecules moving across the interface. The L-J force acts as a resistance to condensation while the electrostatic force, which is predominant in the resultant force, acts as motivity. Meanwhile, some typical molecules which participate in the phase-change process, are especially traced. The results show that the process of condensation leads to a drop of the potential energy of a vapor molecule, which falls into the potential well. Correspondingly, the process of evaporation increases the potential energy of a liquid molecule, which gets over the potential barrier.