T. Thorsteinsson, D. L. Cooper, J. Gerratt, P. B. Karadakov and M. Raimondi.
Theor. Chim. Acta 93, 343-366 (1996).

Abstract

Exact transformations of ‘N electrons in N orbitals’ CASSCF structure spaces are examined that lead to modern valence bond representations, in which the total wavefunction is dominated by covalent structures built from a common product of nonorthogonal orbitals. The resulting descriptions of the electronic structure may be compared directly with those that arise in the spin-coupled (or full-GVB) approach. Using singlet methylene, methane and ozone as representative examples, various overlap-based and energy-based criteria are investigated for generating modern VB representations of ‘N in N’ CASSCF wavefunctions, which we denote CASVB.

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