Density Functional Theory of Molecular Fragments

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Professor Adam Wasserman of Purdue University is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to improve the accuracy and efficiency of electronic structure calculations of properties of molecular systems based on density functional theory (DFT). Dr. Wasserman and his research group are developing a novel density functional theory of molecular fragments, which are parts of larger molecules. They are investigating how the electronic properties of molecules and materials can be calculated from the electron density distortions that occur when chemical bonds are broken or formed. This is important for several reasons: First, the focus on fragments leads to the possibility of carrying out large-scale calculations on parallel supercomputers, allowing for studies that would not be feasible otherwise with present-day computer technology. Second, the focus on fragments allows for new methods that outperform commonly used modern approximations in DFT, especially for systems dominated by so-called strong electron correlations. Third, the focus on fragments allows for accurate computer simulations of systems when chemical bonds are stretched. These systems are ubiquitous in molecular intermediate species of importance to catalytic processes, whose study is beyond the reach of present-day DFT. In addition to training undergraduate and graduate students and developing open-source codes for the scientific community, Dr. Wasserman organizes specialized symposia and develops inter-cultural projects that increase Hispanic participation in scientific research.By adopting a new perspective on DFT without abandoning its core principles, Dr. Wasserman and his research group are improving the accuracy of density-embedding calculations that involve the stretching and breaking of chemical bonds. This is being done via two fronts: (1) The development of physically-motivated approximations to the non-additive pieces of the exchange-correlation energy functional; and (2) The improvement of semi-local Kohn-Sham DFT through new approximations to the non-additive piece of the non-interacting kinetic-energy functional. The work involves applications of the many-body theory of open quantum systems and implementations into broadly available quantum-chemistry software packages.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.