Periodic Coupled Cluster Methods for Optical Activity in Chiral Crystals

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WIth support from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry, Marco Caricato of the University of Kansas will work to develop accurate quantum mechanical methods to simulate the electronic response of solids to external fields, with a direct application to optical activity. These methods are expected to provide highly accurate data for this important electronic property of chiral materials, with a twofold goal: to understand the elusive effect of intermolecular interactions on this property, and to benchmark and improve approximate but computationally efficient methods. Caricato will also develop interpretative tools for structure-property relations that may help define design principles for materials with desired features. These tools will be used to develop reduced-scaling strategies to increase computational efficiency. The broader impact of this proposal hinges on the use of computational chemistry to benefit society both in terms of technological advances and educational opportunities. A deeper understanding of the chiral response of a material may lead to design principles for the rational design of materials with desired properties for targeted applications in growing research fields such as chiral sensing and electronics. Caricato will also develop an outreach initiative to exploit the enormous potential of quantum chemistry simulations for high school education. In collaboration with local high school teachers, Caricato will develop educational modules where the students actively run the simulations and analyze the results. This initiative will hopefully stimulate the enthusiasm for science of high school students in rural and economically disadvantaged areas of the state of Kansas, and inspire them to pursue further training in STEM (science, technology, engineering and mathematics) disciplines. Under this award, the Caricato team will develop linear response-periodic coupled cluster (LR-PCC) methods for crystalline solids, and a tensor decomposition analysis useful for data interpretation as well as computational cost reduction. Although density functional theory (DFT) methods still represent a great compromise between cost and accuracy for solid state calculations, they still suffer from the same drawbacks as for molecules: the quality of the results is system-dependent and individual functionals are not systematically improvable. Particularly problematic is the description of intermolecular interactions, which are fundamental for the overall optical response of a chiral system in the condensed phase. The proposed LR-PCC methods will provide accurate data on the role of intermolecular interactions on the optical activity of solids as well as benchmarking data for the development of functionals and basis sets tailored for this property. At the same time, new approaches for qualitative analysis of the relevant tensors will be developed that may help unravel the elusive structure-property relations in optically active materials. These approaches will be also used to devise reduced-scaling techniques to increase the computational efficiency of the algorithms. These efforts have the potential to lead to general methodologies that can be applied to other electronic properties of solids beyond optical activity.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.