Atomistic Description of Two-Dimensional Hexagonal Close-Packed Critical Nuclei Exhibiting Quantization of the Activation Energy Barrier

Abstract

A simple methodology is employed to demonstrate the manifestation of energy quantization in classical, steady-state nucleation of small, geometrically precise clusters. With the use of recent dispersive kinetic theory outcomes, fresh insights into nonsteady-state nucleation-and-growth processes are also put forth. The impetus for this work stems from the fact that classical nucleation theory (CNT), which is often a poor predictor of nucleation rates, relies on macroscopic, continuous material properties to describe the physicochemical characteristics of the critical nucleus that, in turn, determines the activation energy barrier for nucleation; those quantities are not physically relevant on the atomic/nanometer scale. While it is shown that the low apparent interfacial tension of the smallest critical clusters likely gives rise to a very diffuse interface, their crystalline core provides a natural high-energy (metastable) state useful in determining the activation energy. For simplicity, it is assumed th...