Prediction of absolute crystal-nucleation rate in hard-sphere colloids
Prediction of absolute crystal-nucleation rate in hard-sphere colloids
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DOI：
10.1038/35059035
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发表时间：
2001-02-22
期刊：
影响因子：
64.8
通讯作者：
Frenkel, D
中科院分区：
文献类型：
--
作者：
Auer, S;Frenkel, D
晶体成核是一种被广泛研究的现象，但其发生的速度仍然难以预测。小晶核在过饱和溶液中自发形成，但除非它们的尺寸超过临界值（即所谓的临界核），否则它们将重新溶解而不是生长。事实证明，正是这个限速步骤很难通过实验来探究。晶体成核速率取决于 P-crit（临界核自发形成的（非常小）概率），以及测量临界核随后生长速率的动力学因子 (kappa)。由于缺乏任一量的先验知识，经典成核理论（1）通常用于分析晶体成核实验，调整无约束参数以适应观察结果。这种方法没有得出绝对成核率的“第一原理”预测。在这里，我们从不同的角度解决这个问题，模拟硬胶体球悬浮液中的成核过程，以获得晶体成核速率的定量数值预测。我们发现计算的成核速率与实验（2-4）推导出的成核速率之间存在很大差异：P-crit 的最佳实验估计似乎大了几个数量级。
Crystal nucleation is a much-studied phenomenon, yet the rate at which it occurs remains difficult to predict. Small crystal nuclei form spontaneously in supersaturated solutions, but unless their size exceeds a critical value-the so-called critical nucleus-they will re-dissolve rather than grow. It is this rate-limiting step that has proved difficult to probe experimentally. The crystal nucleation rate depends on P-crit, the (very small) probability that a critical nucleus forms spontaneously, and on a kinetic factor (kappa) that measures the rate at which critical nuclei subsequently grow. Given the absence of a priori knowledge of either quantity, classical nucleation theory(1) is commonly used to analyse crystal nucleation experiments, with the unconstrained parameters adjusted to fit the observations. This approach yields no 'first principles' prediction of absolute nucleation rates. Here we approach the problem from a different angle, simulating the nucleation process in a suspension of hard colloidal spheres, to obtain quantitative numerical predictions of the crystal nucleation rate. We find large discrepancies between the computed nucleation rates and those deduced from experiments(2-4): the best experimental estimates of P-crit seem to be too large by several orders of magnitude.