Non-orthogonal configuration interaction is a powerful and general method to treat ground and excited states of systems that include strong correlation effects. The main challenge is identifying the specific non-orthogonal configurations to include in a way that is not entirely system-specific. The focus of my talk will be describing how to address this question for several classes of excited state problems. One class are valence excitations in molecular complexes, where use of absolutely localized orbitals permits identification of appropriate diabatic states. Another class are core excitations, where the significant failures of CIS can be remedied by the formulation of an appropriate non-orthogonal CIS method. A third class are strongly correlated molecules, where the appropriate diabatic configurations are initialized by localizing the orbitals in a relevant subspace. Assessment of numerical results shows that orbital relaxation effects can be very effectively captured in each of these types of system. If time and progress permit, I will also discuss how these NOCI references can be corrected for the remaining effects of dynamic correlation (this is a significant challenge because each such reference has a different set of orbitals!).

Electronic excited states from non-orthogonal configuration interaction: Valence and core excitations, and strong correlations

256th National Meeting (2018)

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