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首页> 外文期刊>The Journal of Chemical Physics >Liquid-drop formalism and free-energy surfaces in binary homogeneous nucleation theory
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Liquid-drop formalism and free-energy surfaces in binary homogeneous nucleation theory

机译：二元均相成核理论中的液滴形式主义和自由能表面

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Three different derivations of the classical binary nucleation theory are considered in detail. It is shown that the derivation originally presented by Wilemski [J. Chem. Phys. 80, 1370 (1984)] is consistent with more extensive derivations [Oxtoby and Kashchiev, J. Chem. Phys. 100, 7665 (1994)]; Debenedetti, Metastable Liquids: Concepts and Principles (Princeton University Press, Princeton, 1996) if and only if the assumption is made that the surface of tension of the binary nucleus coincides with the dividing surface specified by the surface condition #SIGMA#n_(si)v_(li) = 0, where the n_(si) denote surface excess numbers of molecules of species i, and the v's are partial molecular volumes. From this condition, it follows that (1) the surface tension is curvature independent and (2) that the nucleus volume is V = #SIGMA#n_(li)v_(li) = #SIGMA#g_iv_(li), where the n_(li) are the numbers of molecules in the uniform liquid phase of the droplet model encompassed by the surface of tension, and the g_i are the total molecular occupation numbers contained by the nucleus. We show, furthermore, that the above surface condition leads to explicit formulas for the surface excess numbers n_(si) in the nucleus. Computations for the ethanol-water system show that the surface number for water molecules (n_(s,H_2O)) causes the negative occupation numbers (g_(H_2O)) obtained earlier using the classical nucleation theory. The unphysical behavior produced by the classical theory for surface active systems is thus a direct consequence of the assumption of curvature independent of surface tension. Based on the explicit formulas for n_(si), we calculate the full free-energy surfaces for binary nucleation in the revised classical theory and compare these with the free-energy surfaces in the Doyle (unrevised classical) theory. Significant differences in nucleus size and composition are found between these models and they are related to surface excess density. It is shown that only for the revised classical theory is the nucleus composition consistent with the Gibbs dividing surface model.
机译：详细考虑了经典二进制成核理论的三个不同派生。结果表明，该推导最初是由Wilemski提出的[J．化学物理80，1370（1984）]与更广泛的推导一致[Oxtoby and Kashchiev，J. Chem。物理100，7665（1994）]; Debenedetti，“亚稳液体：概念和原理”（普林斯顿大学出版社，普林斯顿，1996年），且仅当假设二元核的张力表面与表面条件＃SIGMA＃n_（si ）v_（li）= 0，其中n_（si）表示物种i的分子的表面过量数，而v为部分分子体积。根据此条件，可以得出以下结论：（1）表面张力与曲率无关，并且（2）原子核体积为V =＃SIGMA＃n_（li）v_（li）=＃SIGMA＃g_iv_（li），其中n_ （li）是张力表面所包围的液滴模型的均匀液相中的分子数，g_i是原子核所包含的总分子占有数。我们还表明，上述表面条件导致原子核中表面多余数n_（si）的明确公式。对乙醇-水系统的计算表明，水分子的表面数（n_（s，H_2O））导致较早使用经典成核理论获得的负占据数（g_（H_2O））。因此，经典理论对表面活性系统产生的非物理行为是假设曲率与表面张力无关的直接结果。基于n_（si）的显式公式，我们在修正的经典理论中计算了二元成核的全自由能面，并将其与Doyle（未经修订的经典）理论中的自由能面进行了比较。在这些模型之间发现核大小和组成上的显着差异，并且它们与表面过量密度有关。结果表明，只有在修正的经典理论中，原子核组成才与吉布斯分裂表面模型相一致。

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