Huckel-Lewis Projection Method: A Weights Watcher for Mesomeric Structures

A new approach to extract the coefficients and weights of Lewis structures from the Huckel wave function is designed: Huckel-Lewis projection (HL-P). The weights are obtained by projection on overlapping Lewis structures. This straightforward alternative to ab initio approaches is detailed and used on typical cases, including acrolein, allyl radical, pyrrole-like systems, and imidazolylidene. A trust parameter is defined and shown as a guide to retrieve the most important Lewis structures. The emblematic examples of butadiene and benzene are chosen to illustrate the use of this parameter.