CAREER: Resonant Hartree-Fock Inspired Descriptions of Excited State Processes

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With support from the Chemical Theory, Models and Computational Methods (CTMC) Program in the Division of Chemistry and the Established Program to Stimulate Competitive Research (EPSCoR), Lee M. Thompson of University of Louisville is developing computational approaches to simulate excited state processes of relevance to metallo-photocatalysis. Metallo-photocatalysis combines transition metal catalysis and photoredox catalysis to enable new molecular synthesis approaches. However, several competing mechanisms for catalyst activation can potentially lead to different reaction products, and so computational modelling is beneficial to establish the rates of excited state processes and design catalytic systems that enhance the desired reactivity. For this, modeling challenges exist, including: (i) the size of the systems involved, (ii) the nature of the electronic structure of these systems as these are often not amenable to current approximations embodied in reduced-CPU (central processing unit) time methods, and (iii) theoretical formalisms requiring computation of terms that are difficult to extract from simulation. To resolve these difficulties, Dr. Thompson is developing computational methods that couple together low-cost approximations that each capture different features of the electronic structure. The aim is to develop a general computational platform of more accurate approaches that takes advantage of partitioning of the electronic interactions to reduce computational efforts. This project also includes the development of an integrated education plan focusing on programming literacy and sustainable software development that aims to provide students with a deeper understanding of physical chemistry and computational science. The principal investigator is also working to build a forum to engage stakeholders in the chemistry enterprise in Louisville, KY through the Derby lecture series. This project on Resonant Hartree-Fock inspired descriptions of excited state processes consists of two main scientific goals. First, the Thompson research team is developing algorithms that explore self-consistent field (SCF) solution space to understand how the SCF function landscape encodes different correlation mechanisms. The methods permit enumeration of SCF solutions from which a short determinant expansion can be chosen that spans relevant correlation mechanisms present in molecular systems. Additionally, the SCF solutions can be used as references for post-SCF methods. Second, models that optimize a different-orbitals-for-different-configurations wavefunction to account for interactions between the different correlation mechanisms are being designed and implemented. The resulting wavefunction is being used as a platform to recover remaining correlation energy at reduced computational cost. The new methods will be applied to the study of photo-induced electron transfer and excitation energy transfer rates in metallo-photocatalytic systems. These tools, if successful, could have a significant impact on the design of new photoredox catalyst systems and processes, an area of great current interest in reaction development.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.