The valence bond description of conjugated molecules. II. A very simple method to approximate the structural weights of a fully correlated valence bond wavefunction

A very simple method to get the same structural weights as those provided by a fully correlated valence bond function is proposed. It applies to the ground states of delocalized systems, and only requires the knowledge of the occupied molecular orbitals. The SCF wavefunction is projected on a valence bond basis, and the SCF weights thus obtained are multiplied by some sets of multipliers which are transferable from one molecule to another. Some numerical examples are displayed, showing a very satisfying agreement between the structural weights thus estimated and the ones resulting from a rigorous calculation.