Hückel-Lewis projection method: a "weights watcher" for mesomeric structures.

A new approach to extract the coefficients and weights of Lewis structures from the Hückel wave function is designed: Hückel-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.