A critical reexamination of the fundamentals of classical nucleation theory.

摘要

This thesis examines the basic presumptions behind the classic nucleation theory (CNT). Nucleation is the process by which clusters of a stable phase form in a metastable phase. CNT depicts the process as the clusters grow and shrink through the attachment and detachment reactions with monomers ( monomer approximation). It assumes the metastable phase obeys the laws of fluctuation thermodynamics (constrained equilibrium hypothesis ) and partitions a cluster's free energy into a bulk term and a surface term having constant energy density equal to their macroscopic values ( capillarity approximation). With the aid of molecular dynamics (MD) computations that simulate the nucleation of supersaturated Lennard-Jones gas, we discovered that the constrained equilibrium hypothesis and the capillarity approximation do not hold, while the monomer approximation is acceptable due to the breakdown of the detailed balance. We also studied the mechanism behind the binary to unary transition problem (the nucleation rate goes to zero when one component of a binary system diminishes) and provided a simple formula to predict the rate correctly.