ABSTRACT
Why another quantum theory of the matter? Why the Density Functional Theory (DFT)? Its pioneers and promoters, Walter Kohn, Robert G. Parr, and Axel Becke – just to name a few, affirm that modeling electronic density features in 3D real space produces much benefits in both conceptually understanding of bonding as well in electronic localization with a bonding impact for the concerned N-many-electronic systems. The present chapter aims to open a unitarily presentation of the quantum fundaments of DFT as well to prospect directions in electronic bonding, reactivity, bridging with the ultimate approach of bosons-bondons allowing further Bose-Einstein condensation. In DFT, the density and their combinations in the density functionals of the total energy plays a primordial role. It fulfills the N-contingency, assures the total energy minimization, influences the different levels of approximation, that is local density or gradient density frameworks, and controls the bonding through electronic reactivity principles of electronegativity, chemical hardness, and chemical action indices (Putz, 2008a, 2008b, 2008c, 2008d, 2008e; Putz, 2011a, 2011b, 2011c, 2011d). Studying the electronic density properties of electronic systems guaranties the universal treatment of whatever systems, no matter how rich in electrons is, from atoms, to molecules, to solids and aggregates.
