Institut für Theoretische Physik, Universität Leipzig, Postfach 100 920, D-04009 Leipzig, Germany.
Nat Commun. 2017 Feb 27;8:14546. doi: 10.1038/ncomms14546.
A common approach to study nucleation rates is the estimation of free-energy barriers. This usually requires knowledge about the shape of the forming droplet, a task that becomes notoriously difficult in macromolecular setups starting with a proper definition of the cluster boundary. Here we demonstrate a shape-free determination of the free energy for temperature-driven cluster formation in particle as well as polymer systems. Combined with rigorous results on equilibrium droplet formation, this allows for a well-defined finite-size scaling analysis of the effective interfacial free energy at a fixed density. We first verify the theoretical predictions for the formation of a liquid droplet in a supersaturated particle gas by generalized-ensemble Monte Carlo simulations of a Lennard-Jones system. Going one step further, we then generalize this approach to cluster formation in a dilute polymer solution. Our results suggest an analogy with particle condensation, when the macromolecules are interpreted as extended particles.
研究成核速率的一种常用方法是估计自由能势垒。这通常需要了解形成液滴的形状，而在从适当定义团簇边界开始的大分子设置中，这一任务变得非常困难。在这里，我们展示了一种无需考虑形状即可确定粒子和聚合物体系中温度驱动的团簇形成的自由能的方法。与关于平衡液滴形成的严格结果相结合，这允许在固定密度下对有效界面自由能进行明确定义的有限尺寸标度分析。我们首先通过朗道 - 琼斯体系的广义系综蒙特卡罗模拟来验证超饱和颗粒气体中液滴形成的理论预测。更进一步，我们将这种方法推广到稀聚合物溶液中的团簇形成。我们的结果表明，当将大分子解释为扩展粒子时，与粒子凝聚具有类似性。
