Applying Time-dependent Density Functional Theory’s Linear Response to π molecular systems for electronic excitation properties
Predicting excited state molecular properties of an ensemble of molecules in silico is a goalfor theoretical and computational chemists. Solving for these properties with exact and analytical physics is out of reach within a reasonable time-frame, hence approximations are taken. This thesis starts from the approximations of Kohn Sham DFT to determine a reference electronic state for a molecular geometry of classical nuclei, then computing excited electronic states and properties such as gradients using response theory in the framework of TDDFT. While there are well established sets of parameters and approximations that have worked well on particular molecular systems, this thesis presents an investigation of parameters relating to the (1) Krylov subspace approximate solve for excitations, (2) Tully Surface Hopping algorithm for non-adiabatic molecular dynamics, and (3) Excitations of Lanthanide(II) complexes where previous, standard approaches are unsatisfactory. The broader impact is a better understanding of these approaches and parameters, with attention drawn to various algorithmic features that should color interpretation of computed properties for most molecular systems.
In pursuit of understanding chemistry, the chemical sense of intermolecular forces (importantto property predictions described above), has been translated into (4) a card game at the undergraduate general chemistry level. A pedagogy study of the card game was carried out, suggesting that it could improve undergraduate understanding of intermolecular forces.