(36d) New Picture of First-Order Phase Transitions in Metastable Fluids: Homogeneous Nucleation and Growth

Homogeneous nucleation is the activated process by which the new phase (vapor or liquid) is formed from a bulk metastable fluid (superheated liquid or supercooled vapor, respectively) in the absence of impurities or solid surfaces. Recently, we showed that bubble nucleation is more appropriately described by an ?activated instability?. As the free energy barrier is surmounted, further growth of the post-critical bubbles must necessarily proceed via a mechanism appropriate for an unstable system. Ongoing work also indicates that limits of stability also appear for droplet nucleation, though important differences between droplet and bubble formation still remain. We speculate on what the appropriate signature is needed to identify these unstable growth stages. We discuss how some current expressions for the rate of nucleation need to be modified to incorporate the different properties of the free energy surface that emerge from our studies.