On the origin of bonding in metals: sodium and chromium as case studies

Abstract

The bonding in metals is analysed within the framework of the PATMOS (Perturbed AToms in MOlecules and Solids) model. The binding energy per atom is written as a sum of a distortion energy of the atom and the partitioned interaction energy comprising Coulombic, exchange and correlation terms. On the basis of calculations on one-dimensional arrays of sodium and chromium atoms, the following conjecture is suggested. Metals are made of weakly interacting atoms, i.e. perturbed atoms. A proper description of bonding requires an unrestricted Hartree-Fock wave function as the basic approximation. Metals and molecules have in common the predominance of the Coulombic interatomic interaction energy. Electron correlation is of paramount importance.