269b The Role of Critical Cavities in Homogeneous Bubble Nucleation

Mark J. Uline and David S. Corti Previous computational and density-functional theory (DFT) studies[1,2] of cavities (regions devoid of particle centers) within the superheated Lennard-Jones (LJ) liquid revealed that there exists a so-called critical cavity, whereby the presence of cavities with radii larger than some critical radius caused the superheated liquid to become unstable, i.e., phase separate. In addition, the critical cavity was shown by DFT calculations to represent a true thermodynamic limit of stability for the superheated liquid. Furthermore, for the LJ fluid, the size of the critical cavity was found to be a strict lower bound to the size of the critical bubble while the reversible work of forming a critical cavity, Wc, was found to be a strict upper bound to the reversible work of forming a critical bubble, Wb. Wc, like Wb, was also shown to scale in a temperature independent fashion when plotted against the scaling parameter used by Shen and Debenedetti[3] in their DFT study of homogeneous bubble nucleation. These studies reveal a previously unexpected connection between the critical cavity and the critical bubble and suggest that the critical cavity is relevant, to some degree, to the molecular mechanisms of homogeneous bubble nucleation.