Computational Characterizaion of Non-covalent Clusters with New and Existing Methods

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In this project funded by the Chemical Structure, Dynamics and Mechanisms-A (CSDM-A) and Macromolecular, Supramolecular and Nanochemistry (MSN) programs of the Division of Chemistry, Professor Greg Tschumper of the University of Mississippi is using computational tools based on quantum mechanics (QM) to model and study clusters of molecules held together by weak interactions. It is weak interactions that cause atoms and molecules stick to each other without actually forming chemical bonds. Weak interactions include hydrogen bonding, halogen bonding, and London dispersion forces. These computations complement ongoing experimental investigations ranging from fundamental studies of solvation to the design, synthesis and characterization of new molecules, nano-scale assemblies and materials. More broadly, the impact of this work includes accelerating the development of novel materials with potential societal benefits (e.g., clean energy, drug delivery, and compact flexible electronics). This research program has a positive impact on the education and training of science students from underrepresented groups at the graduate and undergraduate levels. Through a collaboration with Professor Jeremy Carr of Central Alabama Community College (CACC), Professor Tschumper provides research experiences for community college students.The project is divided into two parts, the first of which employs well-calibrated methods based on both density functional theory (DFT) and wave function theory (WFT) to a series of computational investigations devised to facilitate experimental characterization(spectroscopic, crystallographic, etc.). The methods make reliable predictions that can aid efforts to design and synthesize new molecules, nano-structures and materials. The second aspect of the research concentrates on the continued development of the N-body : Many-body integrated QM : QM methodology to enable the routine application of high-accuracy QM techniques to larger non-covalent clusters with modest computational resources like those often found in individual research labs or small departments. Emphasis is placed on evaluating spectroscopic properties (e.g.,anharmonic vibrational frequencies and NMR chemical shifts) of non-covalent clusters with systematically convergent techniques within the N-body : Many-body framework as well as extending the accuracy and efficiency of the approach to molecular aggregates containing open-shell, ionic and excited state species.