Molecules in Classical and Quantized Fields: Developing Time-dependent Density Functional and Exact Factorization Methods for Electrons, Ions, and Photons

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Professor Neepa Maitra of Rutgers University at Newark is supported by an award from the Chemical Theory, Models and Computational Methods (CTMC) program in the Division of Chemistry. Maitra and her research group will address some of the fundamental challenges in computational simulations of molecules in classical and quantized light fields by developing new methods for the correlated dynamics of electrons, ions, and photons from first-principles. The projects involve three areas, within which she will develop approximations that should increase the reliability of calculations today: electron dynamics via time-dependent density functional theory, correlated electron-ion dynamics via the exact factorization approach, and their extensions to quantized light-matter interactions for applications to hybrid light-matter states (polaritons). The developments impact applications where knowledge and understanding beyond equilibrium electronic structure are necessary: from photovoltaic design to quantum control of electronic and nuclear dynamics by attosecond and femtosecond laser fields, or by tuning cavity parameters. This project will have a broad educational impact through the training of undergraduate and graduate students in cutting-edge research, co-organizing and participating in summer schools in her research field as well as continuing a Zoom PhD Student Seminar series, and establishing a high school outreach tutoring program to the underserved Newark Public School District to mitigate our society's uneven access to educational resources and promote the development of underrepresented minority scientists.Time-dependent density functional theory for fully non-perturbative processes will be re-cast to require the exchange-correlation functionals only in the linear and quadratic response regimes, where the adiabatic approximations in use today are best suited. Improved approximations derived from exact expressions will be developed. This moves TDDFT towards being as confidently used for real-time non-perturbative processes as it is used for spectra and ground-state properties. Practical exact-factorization-based mixed quantum-classical schemes for correlated electron-ion dynamics after photo-excitation or in the presence of laser fields will be constructed, that include electronic decoherence and wavepacket branching from first-principles. Extension of these methods to polaritonic systems will lead to a fundamental understanding of how field quantization can alter chemical reactions, and to practical mixed quantum-classical methods for the dynamics and control of molecules confined in optical cavities. The research is providing new computational tools and impacts our fundamental understanding of chemical physics, atomic and molecular physics, materials science, and light-matter interactions. Maitra continues to organize summer schools and tutorials. This project will expand student research network connections globally through the Zoom PhD Student Seminars her group initiated last summer. She will establish a high school tutoring program in the Newark Public School district. Mentoring within the group helps guide postdoctoral fellows, graduate, and undergraduate students towards scientifically-oriented futures.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.