Molecular Electronic Structure Theory: Methods and Applications

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Henry (Fritz) Schaeffer is supported by an award from the Chemical Theory, Models and Computational Method program in the Division of Chemistry to develop new computational and theoretical approaches for quantum chemistry. This project contributes to the understanding of atoms, molecules, and molecular assemblies in the gas, liquid, and solid phases. These are the elementary components of the chemistry that underlies our understanding of materials from lasers to superconductors and on to biochemical systems. The most important equation in science, the Schrodinger Equation, is the key to new discoveries in science and engineering, areas dedicated to advances of importance to humankind. While one speaks of the Schrodinger Equation, in fact there is a different Schrodinger Equation for every different molecular system. These equations are extremely complicated for systems of broad, general interest. The practical solutions of the Schrodinger Equation require a profound mastery of both mathematics and physics to allow the derivation of important new methods. Dr. Schaefer and his research team excel in the development and application of mathematical physics, algorithm design, and computer science to achieve these goals. An important new method being developed is density cumulant functional theory. The research group also applies these new methods to the solution of important problems in the chemical sciences. Their research on manganese CO2 reduction, palladium catalysts, silicon chemistry, gallium nitride nanotubes, the CF3 substitutes SF5 and PF4, iodine clusters, and atmospheric chemistry, bears upon several areas of technological concern. This project focuses on the development of new theoretical and computational methods for the understanding and prediction of chemical phenomena. More specifically, the Schaefer group uses electronic structure theory (quantum chemistry) to innovate, implement, and apply new methods for the description of electron correlation in molecules, one of the most challenging areas of chemical theory. A emphasis of this proposal is the development of multi-reference density cumulant theory (MRDCT). The establishment of MRDCT involves the outline of the new formalism, design of effective algorithms, careful coding of the method, and assessment through benchmarks. Applications of new and existing theoretical methods include molecular architectures; spectroscopy (microwave, infrared, electronic, Raman); potential energy surfaces; energetics; reactions via organometallic catalysts (often involving the earth abundant metal manganese); palladium catalysis for C-H bond activation and reductive elimination; examination of the biologically important class of reactions between persulfides (R1SSR2) and sulfides (R2SR4); and collaborations with experiment toward the synthesis of critically important new main group chemistry targets. Broader impacts of the research include the education of a significant number of gifted Ph.D. students (16 in the group currently). Professor Schaefer aggressively and successfully recruits women and underrepresented minorities for their Ph.D. studies. These doctoral students (110 graduated to date, including 23 women) almost uniformly go on to highly fruitful scientific careers in academia, government laboratories, and industry. Schaefer's research group reaches out to local students in elementary, middle, and high schools. The Schaefer group is active in the development PSI4, a freely-available, open source, comprehensive, and widely used suite of quantum chemistry computer programs. It is especially easy for scientists to add new features to the PSI4 code.