Bond metallicity of materials from real space charge density distributions

Abstract

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 ξ J ( r bcp ) = ρ( r bcp )/∇ 2 ρ( r bcp ). In this study we have mined results published using AIM and considered three different local measures of the bond metallicity: the original metallicity definition ξ J ( r bcp ), a dimensionless metallicity indicator, ξ m ( r bcp ), 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 M p X q , where 1 ⩽ p ⩽ 2 and 1 ⩽ q ⩽ 4. A pressure induced non-metallic–metallic phase transitionbonds of the Ge 3N 4 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.