Flagan Richard C
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
J Chem Phys. 2007 Dec 7;127(21):214503. doi: 10.1063/1.2800001.
The traditional theory for binary homogeneous nucleation follows the classical derivation of the nucleation rate in the supposition of a hypothetical constrained-equilibrium distribution in the calculation of the cluster evaporation rate. This model enables calculation of the nucleation rate, but requires evaluation of the cluster distribution and cluster properties for an unstable equilibrium with supersaturated vapor. An alternate derivation of the classical homomolecular nucleation rate eliminated the need for this nonphysical approximation by calculating the evaporative flux at full thermodynamic equilibrium. The present paper develops that approach for binary nucleation; the framework is readily extended to ternary nucleation. In this analysis, the evaporative flux is evaluated by applying mass balance at full thermodynamic equilibrium of the system under study. This approach eliminates both the need for evaluating cluster properties in an unstable constrained-equilibrium state and ambiguity in the normalization constant required in the nucleation-rate expression. Moreover, it naturally spans the entire composition range between the two pure monomers. The cluster fluxes derived using this new model are similar in form to those of classical derivations, so previously developed methods for evaluation of the net nucleation rate can be applied directly to the new formulation.
二元均匀成核的传统理论在计算团簇蒸发速率时，依据假设的约束平衡分布，遵循成核速率的经典推导。该模型能够计算成核速率，但在计算与过饱和蒸汽的不稳定平衡时，需要评估团簇分布和团簇性质。经典同分子成核速率的另一种推导方法，通过在完全热力学平衡下计算蒸发通量，消除了这种非物理近似的必要性。本文将该方法拓展至二元成核；该框架可轻松扩展至三元成核。在此分析中，通过在研究系统的完全热力学平衡下应用质量平衡来评估蒸发通量。这种方法既消除了在不稳定约束平衡状态下评估团簇性质的必要性，也消除了成核速率表达式中所需归一化常数的模糊性。此外，它自然地涵盖了两种纯单体之间的整个组成范围。使用这种新模型导出的团簇通量在形式上与经典推导相似，因此先前开发的评估净成核速率的方法可直接应用于新公式。
