Some Results from Conceptual DFT

A number of concepts for general chemical reactivity exist, such as the principle of hard and soft acids and bases [17, 24], electronegativity [25-27] and frontier orbital theory [28-30]. 

These concepts gained a solid theoretical foundation in density functional theory, namely through the work of Yang and Parr [19-20], Besides its formal beauty, this theory exhibits another nice property The necessary calculations are rather easy to perform. 

Within density functional theory, the chemical potential and the hardness t] become partial derivatives of the system s energy E expressed as a functional of an external potential V(r), i.e., the nuclear conformation, and a function of the number of electrons N  

The respective functional derivative with respect to V(r) yields the electron density p(r). 

It can be shown that the hardness becomes maximal for the densityp(r), which at a given external potential V(r) minimizes the energy E. The hardness is a global parameter related to chemical reactivity, as it does not depend on r. 

---