Kinetics of condensation and boiling: Comparison of different approaches

A comparative analysis of the results of determination of the work of criti cal cluster formation in nucleation theory for three different methods of e valuation-Gibbs' method (employing the capillarity approximation), the van der Waals-Calm and Hilliard method, and a newly developed modified Gibbs ap proach-is given. As a particular application, the processes of condensation and boiling in one-component fluids are analyzed. As a model system for co mparison, van der Waals fluids are chosen. In addition to the work of criti cal cluster formation, the bulk properties of the critical clusters (drops or bubbles), their characteristic sizes, and the values of the surface tens ion are determined in dependence on the initial supersaturation in the syst em or, equivalently, on the size of the critical clusters. It is shown that latter two mentioned methods of determination of the work of critical clus ter formation (the van der Waals-Cahn & Hilliard and the modified Gibbs app roach) lead-at least for the model system considered-to qualitatively and p artly quantitatively equivalent results. Nevertheless, differences remain w hich may lead to quantitative deviations when applied to the determination of the steady-state nucleation rates and further basic characteristics of n ucleation-growth processes. The possible origin of such deviations is discu ssed, and some further directions of analysis are anticipated.