Fukui functions from the relaxed Kohn-Sham orbitals

The global Fukui function of a molecular system, f(r) = (partial derivative rho(r)/partial derivative N)(upsilon), where rho is the ground-state densi ty of a system containing N electrons moving in the external potential upsi lon(r), is calculated within a single Kohn-Sham calculation. It is determin ed by adding to the rigid (frontier orbital) term, relevant for the electro n removal (dN < 0) or addition (dN > 0), the density relaxation contributio n determined from the N-differentiated Kohn-Sham equations. The only approx imation introduced is a neglect of the exchange-correlation terms in the N- derivative of the effective one-body potential. The corresponding equations resulting from the basis set expansion of orbitals are derived, and illust rative results for CO, HCM, H2CO are reported, The predicted Fukui function s for pyrrole, furane, and tiophene are used to diagnose reactivity toward an electrophilic attack. The contour maps of f(r) and the resulting condens ed Fukui function indices are compared with the corresponding \Delta N\ = 1 and the "exact" \Delta N\ --> 0 finite difference predictions.