Hückel theory for Lewis structures: Hückel-Lewis Configuration Interaction (HL-CI)

Weights of Lewis structures can be computed using various ab initio approaches, but this requires some knowledge in using quantum chemistry packages. We present here a straightforward alternative, based on the Interaction between Lewis Configurations and using Hückel energies. Our scheme has been named “Hückel-Lewis CI” (HL-CI) because of these underlying specificities. It provides immediate access to the weights involved in mesomery. Drawbacks of this approach are identified and the accuracy is discussed on typical systems including acrolein, uracil, pyrrole-like systems and imidazolylidene.