 |
Center for Nonlinear Studies |
The molecular orbital picture plays a fundamental role in analyzing and interpreting atoms and molecules' chemical reactivity and spectroscopic behavior. In molecular sciences, molecular orbitals concepts function chiefly as a mnemonic device for recalling data or constructing paradigms. Thus, molecular orbitals pragmatically invoked in these ways serve an inductive purpose: to facilitate the recognition of patterns in molecular structure, properties, energetics, or reactivity. Thus molecular orbitals are servants of a reductionist enterprise that has as its main goal to deduce molecular properties from the principles of quantum mechanics. However, in many cases, orbitals produced by single electron Hamiltonian models such as canonical, Hartree-Fock orbitals may suggest inconsistent molecular properties due to their lack of electronic correlation effects. Thus, in many cases, using the molecular orbital picture is counterproductive in interpreting the molecular properties; different single electron Hamiltonians generate different orbitals that suggest different chemistries for the same molecule. In this talk, by comparing the differences between canonical, Hartree-Fock orbitals, and the correlated normalized Dyson orbitals, I intend to provide a general overview of the importance (or lack thereof) of correlation in the analysis and the interpretation of the electronic structure of molecules. I will also give insights into the importance of electron correlations for chemical interpretations and reactivity justifications based on experimentally verifiable properties to answer the following questions: how significant are electron correlations for chemical interpretations and reactivity justifications based on molecular orbital concepts? Do uncorrelated orbitals and experimental measurements assert the same propositions? Finally, I will suggest procedures to establish uniquely defined orbitals for all molecular systems without sacrificing their ability to reveal relationships between physical and chemical properties, providing new foundations for the development of better qualitative and quantitative theoretical interpretations and predictions in molecular sciences.
Host: Sergei Tretiak