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。冰冻的水存在于大气中——在云中——在云中，矿物尘埃等外来粒子促进了冰的成核。因此，表面辅助冰成核，即非均相冰成核，对云微物理有显著影响。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核是很重要的。尽管已经发展了理论和经验描述，但对于非均相冰成核过程的要求仍然没有完整的描述，也没有框架来先验地知道给定的表面是否会成为良好的冰成核剂。通过实验和模拟的协同努力，将为非均相冰成核的分子水平认识奠定基础。本研究的重点是将表面电荷和晶格匹配与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）模拟将提供云母表面附近水行为的详细见解，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。该研究将为建立非均质冰核预测模型提供基础，该模型可用于与大气化学和天气预报相关的更大尺度模型。本研究开发的模拟工具和结果将为回答bartel - rausch （Nature, 2013）列出的与冷冻水分子行为相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。水系统中由表面辅助的相变与各种领域和过程相关，包括生物组装、表面活性剂、纳米毒理学、半导体工业、食品工业等。同时，本研究也为研究生和本科生提供了多种不同形式的学习机会。这项研究的合作性质和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问题的多种工具。模拟将用于制作资料性录像，作为教育工具，并用于招收科学和工程专业的学生。将开发用户友好的模块，使学生能够执行一些简单的分子模拟，这些模块可以用作课堂讲座的补充，以说明热力学，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，并将在各种国内和国际会议上发表。

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.