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

了解冻结水的分子行为对于预测我们星球的未来至关重要。冻结的水存在于大气中--云中--在那里，矿物尘埃等外来颗粒促进了冰的成核。因此，表面辅助冰成核，即非均质冰成核，对云微物理有着重要的影响。这意味着，为了能够准确地模拟天气和气候，准确地描述异质冰成核是很重要的。虽然理论和经验的描述已经发展，仍然没有完整的描述的非均质冰成核过程的要求，并没有一个框架，知道一个给定的表面是否将是一个很好的冰成核剂的先验.通过协同实验和模拟的努力，为非均质冰成核的分子水平上的理解奠定了基础.本研究的重点将是与表面电荷和晶格匹配的影响，以冰的形成的自由能和成核率的重点异相成核。简单的分子动力学（MD）模拟将提供详细的了解云母表面附近的水的行为，并将与实验结果进行比较。此外，冰成核的动力学和热力学将从模拟计算。这项研究将为建立非均质冰成核的预测模型提供基础，这些模型可以纳入与大气化学和天气预报相关的更大规模模型。开发的模拟工具和这项研究的结果将为回答Bartels-Rausch列出的与冻结水分子行为相关的十大问题中的几个问题提供基础（Nature，2013），这对于预测我们星球的未来至关重要。在水相体系中由表面辅助的相变与包括生物组装、表面活性剂、纳米毒理学、半导体工业、食品工业等在内的各种领域和过程相关。此外，研究还为研究生和本科生提供了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的问题的多种工具。模拟将用于开发信息丰富的视频，用作教育工具以及招募学生进入科学和工程领域。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。这些资料将免费提供给科学界。研究结果将发表在同行评审期刊上，并将在各种国家和国际会议上发表。

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.