  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 (Lutsko, JCP 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 even at high supersaturation nucleation proceeds smoothly
rather than via spinodal-like instabilities as has been suggested recently.
