Department of Physics, University of Helsinki, P.O. Box 64, FIN-00014 Helsinki, Finland.
J Chem Phys. 2011 Nov 21;135(19):194504. doi: 10.1063/1.3662063.
The Becker-Döring kinetic scheme is the most frequently used approach to vapor liquid nucleation. In the present study it has been extended so that master equations for all cluster configurations are included into consideration. In the Becker-Döring kinetic scheme the nucleation rate is calculated through comparison of the balanced steady state and unbalanced steady state solutions of the set of kinetic equations. It is usually assumed that the balanced steady state produces equilibrium cluster distribution, and the evaporation rates are identical in the balanced and unbalanced steady state cases. In the present study we have shown that the evaporation rates are not identical in the equilibrium and unbalanced steady state cases. The evaporation rate depends on the number of clusters at the limit of the cluster definition. We have shown that the ratio of the number of n-clusters at the limit of the cluster definition to the total number of n-clusters is different in equilibrium and unbalanced steady state cases. This causes difference in evaporation rates for these cases and results in a correction factor to the nucleation rate. According to rough estimation it is 10(-1) by the order of magnitude and can be lower if carrier gas effectively equilibrates the clusters. The developed approach allows one to refine the correction factor with Monte Carlo and molecular dynamic simulations.
贝克尔-多林动力学方案是最常用于汽液成核的方法。在本研究中，它被扩展了，使得所有簇构型的主方程都被包括在内。在贝克尔-多林动力学方案中，通过比较动力学方程组的平衡稳态和非平衡稳态解来计算成核速率。通常假设平衡稳态产生平衡的簇分布，并且在平衡和非平衡稳态情况下蒸发速率是相同的。在本研究中，我们已经表明，在平衡和非平衡稳态情况下，蒸发速率并不相同。蒸发速率取决于簇定义极限处的簇数量。我们已经表明，在簇定义极限处的 n-簇数量与总 n-簇数量的比值在平衡和非平衡稳态情况下是不同的。这导致了这些情况下蒸发速率的差异，并导致成核速率的修正因子。根据粗略估计，其量级为 10(-1)，如果载气有效地使簇达到平衡，这个修正因子可以更低。所开发的方法允许使用蒙特卡罗和分子动力学模拟来细化修正因子。
