Atmospheric aerosols nucleate ice in clouds, strongly impacting precipitation and climate. The prevailing consensus is that ice nucleation is promoted heterogeneously by the surface of ice nucleating particles in the aerosols. However, recent experiments indicate that water-soluble molecules, such as polysaccharides of pollen and poly(vinyl alcohol) (PVA), increase the ice freezing temperature. This poses the question of how do flexible soluble molecules promote the formation of water crystals, as they do not expose a well-defined surface to ice. Here we use molecular simulations to demonstrate that PVA promotes ice nucleation through a homogeneous mechanism: PVA increases the nucleation rate by destabilizing water in the solution. This work demonstrates a novel paradigm for understanding ice nucleation by soluble molecules and provides a new handle to design additives that promote crystallization.

中文翻译：

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可溶性分子促进均质冰核化

大气气溶胶使云层中的冰成核，从而强烈影响降水和气候。普遍的共识是，气溶胶中冰核颗粒的表面会异质地促进冰核形成。但是，最近的实验表明，水溶性分子，例如花粉多糖和聚乙烯醇（PVA），会增加冰的冻结温度。这就提出了一个问题，即柔性可溶分子没有将明确定义的表面暴露于冰中，因此如何促进水晶体的形成。在这里，我们使用分子模拟来证明PVA通过均质机制促进冰核化：PVA通过使溶液中的水不稳定来增加冰核化速率。