Exploring Electronic Response Properties of Molecules and Extended Systems using Theoretical Methods

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In this project funded by the Chemical Structure, Dynamics, and Mechanisms (CSDM-A) and Chemical Theory, Models and Computational Methods (CTMC) Programs of the Chemistry Division, Professor Jochen Autschbach of the University at Buffalo, State University of New York and his research team develop and apply quantum theory-based methods in order to learn how light (also known as electromagnetic radiation) can be used to determine the structure of molecules and the internal motions of their atoms and electrons. The Autschbach group is focusing specifically on nuclear magnetic resonance (NMR) spectroscopy and Raman spectroscopy. NMR spectroscopy is a cousin of the magnetic resonance imaging (MRI) technology used in medical diagnostics, and utilizes strong magnetic fields and radio-frequency light to reveal the structure of molecules. In Raman spectroscopy, light (often of visible or ultraviolet wavelengths) is scattered off molecules, and slight changes in the wavelength of the scattered light can provide clues to the vibrational motions of molecules and their overall structure. With the help of sophisticated calculations and computer simulations, the outcome of experimental measurements of these molecular properties are predicted and analyzed. This research advances our understanding of the relationships between molecular structure and measured properties of molecules, as well as our general understanding of the interaction of electromagnetic radiation and matter. Theoretical methods and software developed during this investigation are made available to the larger community of scientists. In addition, this research project provides in-depth training of graduate and undergraduate students, as well as opportunities for summer internships of high-school students. The student experience is enhanced by the collaborative nature of the project: While the research in the PI's laboratory is theoretical and computational in nature, it is carried out in the context of collaborations with experimental researchers from a variety of fields including materials science and catalysis. The molecular properties in question are observed in spectroscopic or optical measurements and of high practical importance to learn about the structures and functions of molecules. The theoretical support provided by the PI is crucial in order to establish and refine the underlying structure-property relationships. Specifically, the properties of interest determine the nuclear magnetic resonance (NMR) and the optical activity of molecules. The theoretical efforts of the project focus specifically on solid-state NMR parameters, NMR relaxation phenomena, and the structural and electronic origins of natural electronic and vibrational optical activity. In addition, the influence of the chemical and physical environment on these molecular properties is explored. NMR relaxation contains a wealth of information about the dynamics and characteristic correlation times of a chemical system. The PI studies the relaxation with ab-initio (from first principles) molecular dynamics simulations, which makes it possible to investigate systems containing elements from all across the periodic table. The optical activity-related part of the project focuses on resonance-effects in Raman vibrational optical activity, that is, when the Raman laser wavelength coincides with an electronic excitation wavelength, and on circularly polarized luminescence. Calculations of solid-state NMR parameters are undertaken to learn how they may reveal the unknown structures of chemical catalysts.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.