Generating a Set of Valence Bond Structures

In the general case, a convenient set of VB structures, on which to project an MO—Cl wave function, cannot include all the VB structures that one could possibly imagine. Such a set would be over-complete (with redundancies), and the result of the projection would not be unique. For the projection to be exact and nonarbitrary, it is necessary to generate a complete and linearly 

A Chemist s Guide to Valence Bond Theory, by Sason Shaik and Philippe C. Hiberty Copyright 2008 John Wiley Sons, Inc. 

It is clear that the first diagrams, 1 and 2, correspond to the familiar Kekule structures, and the three remaining ones, 3—5, to the Dewar structures. 

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