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

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.