The Environmental Chemical Sciences (ECS) program of the Division of Chemistry will support the research program of Prof. Francesco Paesani of the University of California at San Diego. Prof. Paesani and his students will develop and employ new theoretical simulations to model important chemical processes taking place on atmospheric aerosols. The proposed research project aims to gain molecular level understanding of the uptake of water and nitrogen on atmospheric aerosols. These two heterogeneous processes are central for understanding the impacts that aerosol chemistry has on climate and the environment. To realize this goal Prof. Paesani and his students will develop a methodology for molecular-level computer simulations of complex systems which combines a proper treatment of molecular motions at a quantum-mechanical level with a precise ab initio-based description of the underlying multidimensional potential energy surface.
The research project is of great importance to atmospheric sciences. Theoretical methodologies developed during the course of the study will be incorporated into the widely used AMBER software for molecular dynamics simulations through an ongoing active involvement of Prof. Paesani in the AMBER development team. The AMBER software package is currently used by over 500 research groups worldwide and the new methodology developed within this research project will greatly extend the range of applications of molecular simulations in the realm of physical chemistry applied to environmental problems. The study will provide excellent training opportunities to undergraduate and graduate students in an area of research of great societal importance.
A comprehensive understanding of heterogeneous chemical processes taking place on atmospheric particles is key to a quantitative assessment of aerosol impacts on climate, ecosystems, and public health. Within this context, this research has enabled the development and application of new and efficient computational tools for molecular-level modeling of fundamental chemical processes on aerosol particles. Through the development of unique computational approaches, which combine the accuracy of quantum-mechanical theories with the efficiency of molecular-mechanical approaches, our research has led to several discoveries related to the behavior of aqueous systems under atmospheric conditions. These processes are key to the formation and growth of atmospheric particles that affect cloud formation, precipitation, and pollution, which, in turn, have major repercussions on ecosystems and public health. In particular, we shed light on the physical mechanisms that control chemical reactions in solution as well as on aqueous interfaces. Using algorithms based on "machine learning" techniques similar to those adopted by internet search engines, we were able to develop mathematical functions that can represent the interactions between molecules under different conidtions with unprecedented accuracy. Our computational approaches are now available in some of the most popular software for molecular simulations, which thus allow general users to have acces to an efficient computational platform for simulation studies of complex chemical processes, with possible areas of application that include energy transfer and storage, molecular sensing of pollutants and toxicants, catalysis, and drug discovery. This research has involved the training and education of several undergraduate and graduate students as well as postdoctoral scholarshave acquired a solid foundation in theoretical, physical, and computational chemistry. In addition, throughout the entire funding period, students from several high schools in the San Diego County have visited the Paesani lab to learn about and perform molecular simulations of chemical processes of relvance to climate research. All undegraduate and graduate students, and postdocs involved in this project have had the opportunity to learn first hand modern computational techniques as well as to work on the development and implementation of new algorithms for molecular simulations. Considering that in less than 50 years, computers have influenced every aspect of our lives, the activities carried out as part of this research project have significantly broaden student and postdoc's scientific background, enhancing their competitiveness in a fast-growing technological world. The Paesani group has also been directly involved in the "SEA Days" activities at the Birch Aquarium (La Jolla, CA), which focus on multi-generational learning about cutting-edge research related to climate and the environment.