  The mechanism of superstability of nanobubbles in liquid confirmed by many
experimental studies is still in debate since the classical diffusion predicts
their lifetime on the order of a few microseconds. In this work, we study the
requirement for bulk nanobubbles to be stable by using molecular dynamics
simulations. Periodic cubic cells with different cell sizes and different
initial radii are treated to simulate the nanobubble cluster, providing the
equilibrium bubble radius and the interbubble distance. We find out that for
nanobubble with a certain radius $R$ to be stable, the interbubble distance
should be smaller than the maximum interbubble distance $L^*$ being
proportional to $R^{4/3}$.
