Surface Tension and Stability of a Nanobubble in Water: Molecular Simulation

Abstract

Molecular dynamics simulations were carried out for a nanoscale spherical bubble in water at room temperature. The pressure difference between inside and outside of the bubble was investigated and the surface tension was evaluated with assumption of the Young-Laplace (Y-L) equation. The obtained surface tension shows little dependence on the bubble size and agrees with that of flat surface. Thus it is confirmed that the Y-L equation holds for nanobubbles in water. Based on the Y-L equation and the density-dependence of the liquid pressure, mechanical stability of a bubble in a finite system was discussed. The existence of mechanical instability leads to a mechanical definition of critical nucleus size in cavitation nucleation.