Density functional theory of inhomogeneous liquids. III. Liquid-vapor nucleation

The process of nucleation of vapor bubbles from a superheated liquid and of liquid droplets from a supersaturated vapor is investigated using the modified-core van der Waals model density functional theory [J. F. Lutsko, J. Chem. Phys. 128, 184711 (2008)]. A novel approach is developed whereby nucleation is viewed as a transition from a metastable state to a stable state via the minimum free energy path, which is identified using the nudged elastic-band method for exploring free energy surfaces. This allows for the unbiased calculation of the properties of sub- and super-critical clusters, as well as of the critical cluster. For Lennard-Jones fluids, the results compare well to simulation and support the view that at low to moderate supersaturation nucleation proceeds smoothly rather than via spinodal-like instabilities as has been suggested recently. The possibility that the nucleation barrier vanishes at high supersaturation is, however, not ruled out.