Prof. Gregory Tschumper Professor of Chemistry and Biochemistry University of Mississippi Learn more about Prof. Tschumper and his work Tuesday, October 3, 2023 - 11:10am iSTEM Building 2, Room 1218 Departmental Colloquium Mulliken Lecture The subjects of solvation, molecular recognition and supramolecular self-assembly provide some of the motivation and impetus for the work that is the focus of the talk. Convergent approaches to quantum mechanical (QM) ab initio electronic structure calculations have provided tremendous insight into the structures, energetics and spectroscopic signatures of molecular clusters held together by relatively weak, non-covalent interactions (London dispersion forces, hydrogen bonding, halogen bonding, π-stacking, etc.). Unfortunately, the computational demands associated with the most accurate and reliable QM methods often prohibit their application to large molecular systems. Part of this talk will focus on strategies that systematically converge toward exact numerical solutions of the electronic Schrödinger equation via methodical application of correlated wave function methods and Gaussian atomic orbital basis sets. That will set the stage for an overview of computational techniques for non-covalent clusters that take advantage of the many-body expansion (MBE) of the total energy. A layered, ONIOM-like approach to the MBE is one such technique that we have been using to extend demanding QM electronic structure computations, such as the CCSD(T) method, to larger clusters. Some recent applications of both approaches will be discussed.