SPIN DENSITY OF SPIN-FREE VALENCE BOND WAVE FUNCTIONS AND ITS IMPLEMENTATION IN VB2000

Abstract

The expressions for computing the spin density of spin-free valence bond wave functions are derived based on the bonded tableaux approach. The new expressions, although similar to the original forms given by Cooper and McWeeny in the 1960s, are simpler and thus easier for coding. The new formulation was implemented in VB2000, an ab initio valence bond program based on algebrant algorithm and group function theory. The spin density calculation for multi-group VB wave functions is also briefly discussed. As examples of applications, the spin densities of allyl radical and diazide anion [Formula: see text] were computed at different VB levels.