Molecular Dynamics Simulation of Vapor Bubble Nucleation in 2D Lennard-Jones Fluid Along Nanometer-Sized Cavities

Heterogeneous vapor bubble nucleation was numerically simulated on surfaces containing nanometer-sized rectangular cavities of various sizes (ranging from 2.72–9.36 nm width & 4.09–8.34 nm depth). Non-equilibrium molecular dynamics simulations at constant wall temperature were carried out for the two-dimensional (2D) Lennard-Jones (LJ) fluid which was in thermal contact with LJ solid wall. Nucleation was induced by expanding the system volume to a metastable state while keeping the temperature of the solid wall constant. When the aspect ratio (depth-to-width) of the cavity was large (∼3-to-1), the nucleation rate was increased nearly three-fold compared to the flat surface for relatively large wettability; however, the nucleation rate was nearly the same for lower wettability surfaces. Nucleation was generally favored within the cavities due to the stabilization of the cavity side-walls. The value of cutoff radius, wall temperature, and solid-liquid wettability was varied to determine their effect on nucleation rate. The 2D model was validated by comparing thermodynamic averages of pressure and potential energy to predicted values from a 2D LJ equation of state.