Collaborative Research: Heterogeneous Ice Nucleation in Clouds: A Synergistic Experimental and Simulation Approach

了解冰冻水的分子行为对于预测我们星球的未来至关重要。在大气中--云中--存在着冰冻的水，在那里，矿物尘埃等外来颗粒促进了冰核的形成。因此，表面辅助冰成核，即非均质冰成核，对云微物理有重要影响。这意味着，为了能够准确地模拟天气和气候，准确地描述非均质冰成核是很重要的。虽然已经有了理论和经验的描述，但对于非均相成冰过程的要求仍然没有完整的描述，也没有一个框架来先验地知道给定的表面是否是好的成冰剂，通过协同实验和模拟的努力，将为从分子水平上理解非均质成冰奠定基础。这项研究的重点将是将表面电荷和晶格匹配对冰的非均相成核的影响联系起来，重点是形成自由能和成核速率。直接的分子动力学(MD)模拟将提供对云母表面附近水行为的详细了解，并将与实验结果进行比较。此外，还将通过模拟计算冰成核的动力学和热力学。这项研究将为建立非均匀冰核的预测模型提供基础，这些模型可以被纳入与大气化学和天气预报相关的更大规模的模型中。开发的模拟工具和这项研究的结果将为回答Bartels-Rausch(自然，2013)列出的与冻水分子行为有关的十大问题中的几个问题提供基础，这些问题对于预测我们星球的未来至关重要。水相体系中的表面辅助相变与生物组装、表面活性剂、纳米毒理学、半导体工业、食品工业等广泛的领域和过程有关。此外，研究还为研究生和本科生提供了几种不同形式的学习机会。这项研究的合作性质以及两个科学家小组之间的交流计划将使学生接触到用于研究大气化学中具有挑战性的问题的多种工具。模拟将被用于制作信息丰富的视频，作为教育工具以及招收学生进入科学和工程专业。将开发一些用户友好的模块，使学生能够执行一些简单的分子模拟，这些模拟可以作为课堂讲课的补充，说明热力学、动力学和材料的概念。这些将免费提供给科学界。这项研究的结果将发表在同行评议的期刊上，并将在各种国家和国际会议上公布。

Understanding the molecular behavior of frozen water is essential for predicting the future of our planet. Frozen water is present in the atmosphere -- in clouds -- where foreign particles such as mineral dust promote ice nucleation. Consequently, surface-assisted ice nucleation, i.e. heterogeneous ice nucleation, has a significant effect on cloud microphysics. This implies that it is important to accurately describe heterogeneous ice nucleation in order to be able to accurately model the weather and climate. Though theoretical and empirical descriptions have been developed, there is still no complete description of the requirements of the heterogeneous ice nucleation process, and no framework to know a priori if a given surface will be a good ice nucleating agent.Through the synergistic experimental and simulation efforts, the foundation for molecular level understanding of heterogeneous ice nucleation will be built. The focus of this research will be to relate the effects of surface charge and lattice match to heterogeneous nucleation of ice with an emphasis on the free energy of formation and the nucleation rate. Straightforward molecular dynamics (MD) simulations will provide detailed insights into water behavior near mica surfaces and will be compared with experimental findings. In addition, the kinetics and thermodynamics of ice nucleation will be calculated from simulations. The research will provide the basis for building predictive models of heterogeneous ice nucleation that can be incorporated into larger scale models relevant to atmospheric chemistry and weather prediction.The simulation tools developed and results of this research will provide the basis to answer several of the top 10 questions related to molecular behavior of frozen water as listed by Bartels-Rausch (Nature, 2013), which are essential for predicting the future of our planet. Phase transitions assisted by surfaces in aqueous systems are relevant to a wide variety of fields and processes including biological assemblies, surfactants, nanotoxicology, semiconductor industry, food industry and others. Also, the research presents several learning opportunities for graduate and undergraduate students in different forms. The collaborative nature of this research and the exchange program between the two scientist groups will expose the students to a multitude of tools used to study challenging problems in atmospheric chemistry.The simulations will be used to develop informative videos to be used as educational tools as well as for recruitment of students into science and engineering. User-friendly modules that enable students to perform some simple molecular simulations, which can be used as supplements for class lectures to illustrate concepts in thermodynamics, kinetics and materials will be developed. These will be available to the scientific community free-of-charge. The results from the research will be published in peer-reviewed journals and will be presented in various national and international meetings.