Electron distribution and chemical bonding in M3(XO4)2 molecules (M = Mg, Cu; X = P, V) as determined by Ab initio calculations

Ab initio quantum-chemical calculations of cage molecules M₃(XO₄)₂ (M = Mg, Cu; X = P, V) have been carried out. Interatomic interactions in them are quantitatively characterized based on analysis of the electronic properties at the critical points in electron density. The Mg-O interaction is close to pure closed-shell interactions, whereas the other interactions can be treated as intermediate with different degrees of covalence. The specific features of the electronic structure of the molecules are revealed with the use of the electron pair localization function. The arrangement of electron pairs in the outer shells of the cores of the transition metals Cu and V corresponds to the Gillespie model of the regions of local concentration of electrons located opposite the ligands, which illustrates the mechanism of bonding of atoms of the third and subsequent periods of the periodic table.