Variational principles for describing chemical reactions: The Fukui function and chemical hardness revisited

The fundamental principles of density functional theory are applied to achi eve a better understanding of Various theoretical tools for describing chem ical reactivity. Emphasis is given to the Fukui function, the central site restetivity index of density functional theory, which is approached through its own variational principle. A maximum hardness principle is then develo ped and discussed. To make contact with an earlier proof of a maximum hardn ess principle, changes in chemical potential are considered.