CAREER: EXTENDING GROUND STATE QUANTUM CHEMISTRY TO EXCITED STATES

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Eric Neuscamman of the University of California, Berkeley is supported by an award from the Chemical Theory, Models and Computational Methods Program in the Division of Chemistry to develop new theoretical models to describe molecules that are excited by the absorption of light. Interactions with light are fundamental to chemistry. Lasers, for example, play a central role in molecular diagnostics. The absorption of light and its conversion to electricity is central to solar power and to many of the sensory devices used to guard against chemical and biological threats. Scientists are still unable to answer many critical questions about the behavior of molecules that have absorbed light. By constructing theoretical models to describe light-activated molecules, Neuscamman's research provides insights that complement and enhance experimental methods. Neuscamman is also building a multi-level outreach and education effort. His program uses learn-by-playing and learn-by-teaching principles to improve numerical optimization concepts and methods across K-12 education. This effort centers around the design and deployment of age-appropriate games, such as "program your own virtual robot" for high school students. A key feature of this outreach is vertical integration, in which older students, especially undergraduates and high school students, are recruited into the outreach efforts targeting younger students, thus enabling learning-by-teaching. Together, these efforts give students a head start in numerical methods thinking and real-world applications that prepare them for formal calculus training and provide them with the required mathematical skills for scientific endeavors. The ground state variational principle is the single most important theoretical tool in quantum chemistry, allowing wave function approximations and their orbital shapes to be tailored for the ground state of a specific molecule. Historically, the modeling of a large variety of chemical processes has been hampered by the lack of analogous tools for excited states. Such excited states play central roles in understanding light harvesting, atmospheric processes, and energy storage. Although quantum Monte Carlo methods are able to work directly with rigorous excited state variational principles, they have important limitations and do not, at present, benefit from the same quantum-Monte-Carlo/quantum-chemistry synergies that exist for ground states. Professor Neuscamman is extending the advantages of excited state variational principles into the ecosystem of traditional quantum chemistry. This project begins with an excited-state-specific mean field theory that is a direct generalization of Hartree Fock Theory. Professor Neuscamman is developing new excited state generalizations of correlation theories like M'ller Plesset theory and coupled cluster theory. These methods act both as natural partners for Monte Carlo methods and as powerful tools in their own right. In summary, Neuscamman's work generalizes excited state variational principles beyond the world of quantum Monte Carlo in order to bring traditional ground state quantum chemistry to bear on excited state problems.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.