Surface Topology of the Ion-Induced Vapor Nucleation Rate

Abstract

ABSTRACT Ion-induced nucleation involves additional electrostatic interactions between vapor molecules (atoms) and ions. The electrostatic force helps to form the ion stabilized prenucleation embryos and lowers the free energy barrier for nucleation. The free energy for ion-induced critical embryos formation has been calculated using the Thomson's term in the framework of the classical theory of nucleation. Nucleation theory has made obvious progress, but the understanding of the nucleation phenomenon is far from complete. Some ideas for the identification of possible new directions to improve both homogeneous and heterogeneous nucleation theories can be found by analyzing the topology of nucleation rate surfaces. The creation of the ion-induced nucleation rate surfaces is based on the knowledge of phase state diagrams, experimental results on ion-induced nucleation, and a few plausible assumptions. In this article the surfaces of the ion-induced nucleation rates for metastable vapor nucleation will be constructed. Semiempirical rules are formulated for the ion-induced vapor nucleation based on both known experimental and theoretical results. By using surface topology analysis, problems in heterogeneous nucleation theory can be formulated more clearly, and future directions for improvements can be discussed. A point on the spinodal line was found by extrapolation of the logarithm of the actual vapor pressure for ion-induced and homogeneous nucleation at a constant nucleation rate as a function of inverse temperature. Nucleation rate scaling of the surface should yield a quantitative scale for the ion-induced nucleation rates. Phase diagrams need to be incorporated into the interpretation of experimental and theoretical results on ion-induced nucleation.