Challenging chemical concepts through charge density
C. Gatti
Istituto di Scienze e Tecnologie Molecolari del CNR, via Golgi 19, Milano, Italy
* E-mail: c.gatti@istm.cnr.it

Being based on a quantum observable and measurable quantity, the Electron Density (ED) based descriptors retain the advantage of enabling a direct comparison of theoretical predictions with experimental results. They also provide a description of chemical paradigms which is, in principle, freed at the outset from any model preconception or arbitrariness. Furthermore, because of their nature rooted in physics, they are, in turn, ideally suited to validate or possibly reject  the interpretive models of chemistry based on useful, but arbitrary objects.  
	In this lecture, I will apply a number of such descriptors, including the Source Function, the Reduced Density Gradient and the standard tools of the Quantum Theory of Atoms in Molecules to discuss a number of challenging chemical issues, like the Concept of Hypervalency in K2SO4 crystal, the nature of bonding in the Xe oxides crystals at very high pressure, the “signs” of  non-covalent interactions and of electron correlation effects in molecular crystals. For most of these examples, a comparison between X-ray diffraction and ab-initio derived results will also be offered.