Goddards Generalized VB

Goddard[21] made the earliest important generalization to the Coulson-Fisher method. Goddard s generalized VB (GGVB) wave function is written in terms of orbitals that are linear combinations of the AOs. Using the genealogical set of spin functions in turn and 

In simple cases the Gl is a HLSP function while the Gf wave function is a standard tableaux function, which we describe below in Sect. 3.3. For Gf wave functions one may show that the above orthogonality requirement is not a real constraint on the energy. On the other hand, no such invariance occurs with Gl or HLSP functions, so the orthogonality constraint has a real impact on the calculated energy in this case and with all other Gi wave functions. 

Goddard and his coworkers applied the method to a number of chemical problems with an emphasis on orbital following results. 

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