Kashchiev Dimo, Vekilov Peter G, Kolomeisky Anatoly B
Institute of Physical Chemistry, Bulgarian Academy of Sciences, Ul. Acad. G. Bonchev 11, Sofia, Bulgaria.
J Chem Phys. 2005 Jun 22;122(24):244706. doi: 10.1063/1.1943389.
When the nucleation of a stable crystalline phase directly in a supersaturated old phase is greatly retarded, the crystal nuclei might nucleate within faster-forming particles of an intermediate phase. Here we present a theoretical investigation of the kinetics of this two-step nucleation of crystals and derive general expressions for the time dependence of the number of crystals nucleated within the particles of the intermediate phase. The results reveal that crystal nucleation can be strongly delayed by the slow growth of the particles and/or by the slow nucleation of the crystals in them. Furthermore, the linear part of the time dependence of the number of nucleated crystals is determined by the formation rate of the intermediate particles. This is in contrast with the one-step nucleation of crystals when this linear part is determined by the rate of crystal nucleation directly in the old phase. Criteria are proposed for distinction between the one- and two-step nucleation mechanisms, based on the supersaturation dependence of the delay time for nucleation. The application of the theoretical approach to the analysis of experimental data on the nucleation of crystals and other ordered aggregates of protein and other soluble materials is discussed.
当在过饱和旧相中直接形成稳定晶相的成核过程被极大延迟时，晶核可能在中间相形成更快的颗粒内成核。在此，我们对晶体的这种两步成核动力学进行了理论研究，并推导了中间相颗粒内成核晶体数量随时间变化的一般表达式。结果表明，颗粒的缓慢生长和/或其中晶体的缓慢成核会强烈延迟晶体成核。此外，成核晶体数量随时间变化的线性部分由中间颗粒的形成速率决定。这与晶体的一步成核形成对比，在一步成核中，该线性部分由直接在旧相中晶体的成核速率决定。基于成核延迟时间对过饱和度的依赖性，提出了区分一步和两步成核机制的标准。讨论了该理论方法在分析晶体以及蛋白质和其他可溶性材料的其他有序聚集体成核实验数据中的应用。
