General framework for nonclassical nucleation
General framework for nonclassical nucleation
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DOI：
10.1088/1367-2630/aad170
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发表时间：
2018-08
影响因子：
3.3
通讯作者：
M. Durán-Olivencia;P. Yatsyshin;S. Kalliadasis;J. Lutsko
中科院分区：
文献类型：
--
作者：
M. Durán-Olivencia;P. Yatsyshin;S. Kalliadasis;J. Lutsko
大量的实验证据表明，通过中间亚稳态的出现和随后的转变，以多阶段的方式发生广泛的相变。这种多级机制不能在经典成核框架的范围内解释。因此，迫切需要开发新的理论工具来解释这些普遍存在的中间阶段的发生和性质。在这里，我们概述了一个统一的和自洽的理论框架来描述经典和非经典成核。我们的框架提供了一个详细的解释，整个多级成核途径，特别是该途径涉及一个单一的能量障碍，它通过一个致密的阶段，从低密度的初始阶段，达到最终的稳定状态之前。此外，我们表明，亚临界集群内的物质的动力学有利于形成具有中间密度的成核集群，即成核前体。值得注意的是，这些成核前体是不相关的热力学势的局部最小值，通常假设在以前的唯象方法。相反，我们发现它们的出现是由于热力学和动力学之间的竞争集群形成。因此，发现的机制形成的中间阶段可以用来解释最近报道的实验结果在结晶：到目前为止，这些阶段被认为是一些复杂的能量景观与多个能量最小值的后果。使用动力学和热力学的基本概念，我们提供了一个令人满意的解释，在实验中观察到的所谓的非经典成核途径。
A great deal of experimental evidence suggests that a wide spectrum of phase transitions occur in a multistage manner via the appearance and subsequent transformation of intermediate metastable states. Such multistage mechanisms cannot be explained within the realm of the classical nucleation framework. Hence, there is a strong need to develop new theoretical tools to explain the occurrence and nature of these ubiquitous intermediate phases. Here we outline a unified and self-consistent theoretical framework to describe both classical and nonclassical nucleation. Our framework provides a detailed explanation of the whole multistage nucleation pathway showing in particular that the pathway involves a single energy barrier and it passes through a dense phase, starting from a low-density initial phase, before reaching the final stable state. Moreover, we demonstrate that the kinetics of matter inside subcritical clusters favors the formation of nucleation clusters with an intermediate density, i.e. nucleation precursors. Remarkably, these nucleation precursors are not associated with a local minimum of the thermodynamic potential, as commonly assumed in previous phenomenological approaches. On the contrary, we find that they emerge due to the competition between thermodynamics and kinetics of cluster formation. Thus, the mechanism uncovered for the formation of intermediate phases can be used to explain recently reported experimental findings in crystallization: up to now such phases were assumed a consequence of some complex energy landscape with multiple energy minima. Using fundamental concepts from kinetics and thermodynamics, we provide a satisfactory explanation for the so-called nonclassical nucleation pathways observed in experiments.