Proceedings - Interdisciplinary Center for Nanotoxicity

Conference on Current Trends in Computational Chemistry 2009
Using Semiempirical Wavefunctions to Model Properties of
Extended Conjugated Systems
Bijay Bhattarai and William A. Parkinson
Department of Chemistry and Physics, Southeastern Louisiana University,
Hammond LA 70402
The semiempirical wavefunction, particularly Spectroscopic ZINDO (ZINDO/S), has long
been successfully employed for the prediction of uv‐visible spectrum of extended ring systems
via single‐excitation CI. Through perturbation theory, properties such as polarizabilities,
hyperpolarizabilities and NMR parameters are normally written as functions of the energy
difference between the ground and excited states. As such, ZINDO/S should provide a
reasonable approximation in evaluating such expressions. In this study, we examine
computational approaches for employing ZINDO/S energy representations in second‐ and
higher‐order property evaluations, while still maintaining the economy of the semiempirical SCF
procedure. We also look at various parameterizations of transition moments for electric field
and NMR Hamiltonians that lead to conclusions that trend with experiment.
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