Bond metallicity of materials from real space charge density distributions

Within the framework of the theory of atoms in molecules, AIM, it was recently proposed that the metallicity of a bond could be determined from the properties of the electron density at the bond critical point using the ratio ξJ(rbcp)=ρ(rbcp)/∇2ρ(rbcp). In this study we have mined results published using AIM and considered three different local measures of the bond metallicity: the original metallicity definition ξJ(rbcp), a dimensionless metallicity indicator, ξm(rbcp), and the value of Bohm’s quantum potential at the bond critical point. A global measure of metallicity, the planarity index f, has also been examined. We focus this study on a broad range of elements, ions and compounds of the form of the later is Mp Xq, where 1⩽p⩽2 and 1⩽q⩽4. A pressure induced non-metallic–metallic phase transitionbonds of the Ge3N4 for the β- and γ-crystals is observed. The various metallicity measures agree well with experimental observations and are observed to give qualitatively similar results.