Molecular dynamics study on phase equilibrium around vapor bubbles in low-density liquid argon

In this study, we investigate the vapor bubble stability in liquid argon using a molecular dynamics simulation. The Lennard-Jones (L-J) interparticle interaction potential is used to simulate the interaction forces between argon molecules. The discrimination method based on Stillinger's cluster criterion is employed to classify the vapor molecules evaporated from the bulk liquid. In this criterion, the vapor molecules are determined to have no neighboring molecules within a 1.23 to 1.32σ radius, where σ is the interaction radius in the L-J potential. It is found that the spherical bubble shape is maintained and the Young-Laplace equation applies mainly as a result of the large negative pressure of the liquid. The 10-90 thickness of the vapor-liquid interface was approximately 30 to 90% of the bubble radius in the present simulation. A certain frequency of condensation and evaporation was maintained in the smaller bubble case, which is not proportional to the decrease in bubble surface area.