RII Track-4:NSF: Unveiling the structure and thermodynamic stability of pre-nucleation clusters and their role in multistep nucleation

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Nucleation influences the subsequent crystallization process which impacts our daily life. However, its mechanism remains poorly understood due to limited characterization. The purpose of the research is to identify what occurs at the early stage of nucleation of salt solutions. The proposed work will overcome the current barriers using innovative experimental apparatus enabled by the fellowship. The results of this project will advance the current knowledge on what occurs in the early stage of nucleation, which will lead to a better understanding of the nucleation mechanism of salt solutions. The fellowship project will result in new multidisciplinary collaborations among Iowa State University, the University of Iowa, Ames Laboratory, and Oak Ridge National Laboratory. One doctoral student will acquire skills in molecular dynamics simulation and gain extensive hands-on experience. Two undergraduate students from the Society of Hispanic Professional Engineers (SHPE) will join the project and present their work at the SHPE National Convention. Three existing outreach programs at Iowa State University will be leveraged to share the fellowship project with K-12 students, teachers, and parents. A growing number of materials, including proteins, electrolyte solutions, biominerals, and colloids, have been observed to nucleate in multistep forming pre-nucleation clusters (PNCs) prior to nucleation. It is apparent that PNCs play a critically important role in multistep nucleation (MSN), yet their nature is poorly understood. The rationale for the proposed research is that a mechanistic understanding of MSN is likely to provide new opportunities to develop a method to control the nucleation and growth of desired crystal phases. For this reason, the project aims to identify the structure, thermodynamic stability, and role of PNCs in an aqueous NaCl solution. The PI team will overcome the current experimental obstacles by integrating the solution electrostatic levitator (SEL) developed by the PI team with neutron scattering at Oak Ridge National Laboratory. The long-term goal of the project is to develop a predictive framework to anticipate and control the MSN in various aqueous solutions. The proposed research will lead to a vertical-step advancement towards elucidating the mechanism of MSN in electrolyte solutions and would give deeper insights to better understand the MSN in other material systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.