CHALLENGING QUESTIONS IN CHEMISTRY: THE SYNERGIC ROLE OF AB-INITIO CALCULATIONS, X-RAY DERIVED CHARGE DENSITIES AND MODERN TOPOLOGICAL APPROACHES TO BONDING

This work deals with the role ab-initio calculations have in supporting and, when needed, helping to clarify the meaning of experimental findings. Furthermore, the extra information one gets from the wavefunction, that is the knowledge of the density matrix and of the pair density, both customarily unavailable from experiment, has revealed of uttermost importance in the study of the challenging chemical bond features investigated in this thesis. The charge densities of FeX2 marcasitic compounds, of crystalline K2SO4 and of a reference compound for magnetically active coordination polymers Zn(HCOO)2(H2O)2 have been analysed from both the experimental and crystallographic point of view.