结晶的微观方法：挑战经典/非经典二分法
A microscopic approach to crystallization: challenging the classical/non-classical dichotomy
AI总结：
本研究扩展了基于涨落流体动力学和经典密度泛函理论的成核框架，用于描述非经典成核动力学，发现尽管路径非经典，但团簇大小仍是主要序参量，且经典成核理论在某些情况下仍适用。
摘要：
最近研究表明，基于涨落流体动力学和经典密度泛函理论的成核理论描述可用于确定结晶的非经典成核路径（Lutsko, Sci. Adv. 5, eaav7399 (2019)）。该方法的优势在于不依赖任何关于序参量的假设，且除了分子相互作用势外无需其他输入。我们现在扩展这一基本框架，以描述非经典成核的动力学。我们使用两种不同的相互作用势，研究胶体颗粒低浓度溶液中液滴和晶体固体的成核过程。我们发现，在成核早期阶段，液滴和晶体的成核路径非常相似，直到由于固体路径上的快速有序化而出现分歧，这与“非经典”结晶的范式一致。我们计算了临界团簇处的不稳定模式，发现尽管固体成核具有非经典性质，但在所有情况下，成核团簇的大小仍然是主要的序参量，这支持了结晶“动力学”的“经典”描述。我们展示了可以从我们的形式化方法中系统地提取成核速率。我们的结果表明，在某些情况下，尽管成核路径具有非经典性质，经典成核理论仍可为固体提供合理的结果，但在某些情况下它可能会失效。这为最近的实验和模拟工作提供了细致入微的视角，这些工作表明晶体成核的重要方面可以在经典框架内描述。
英文摘要：
Recently, it was shown that a theoretical description of nucleation based on fluctuating hydrodynamics and classical density functional theory can be used to determine non-classical nucleation pathways for crystallization (Lutsko, Sci. Adv. 5, eaav7399 (2019)). The advantage of the approach is that it is free of any assumptions regarding order parameters and that requires no input other than molecular interaction potentials. We now extend this fundamental framework so as to describe the dynamics of non-classical nucleation. We use it to study the nucleation of both droplets and crystalline solids from a low-concentration solution of colloidal particles using two different interaction potentials. We find that the nucleation pathways of both droplets and crystals are remarkably similar at the early stages of nucleation until they diverge due to a rapid ordering along the solid pathways in line with the paradigm of "non-classical" crystallization. We compute the unstable modes at the critical clusters and find that despite the non-classical nature of solid nucleation, the size of the nucleating clusters remains the principle order parameter in all cases supporting a "classical" description of the {\it dynamics} of crystallization. We show that nucleation rates can be extracted from our formalism in a systematic way. Our results suggest that in some cases, despite the non-classical nature of the nucleation pathways, classical nucleation theory can give reasonable results for solids but that there are circumstances where it may fail. This contributes a nuanced perspective to recent experimental and simulation work suggesting that important aspects of crystal nucleation can be described within a classical framework.
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