The Spin-Free Valence Bond Method Applications to Metallic and Electron Rich Systems

The spin-free valence bond method applications to metallic and electron rich systems 

We discuss the application of the valence bond method to systems with delocalized bonds, namely, metallic and anionic systems. We show that the admittance of extra orbitals in these systems is necessary, leading to new types of structures, which are related to processes of charge transfer. 

According to Pauling [6-9], valence bond theory can also be used to describe metallic systems. At a first glance, this seems to be contradictory, since VB deals with localized chemical bonds and a metallic bond is thought of as completely delocalized. Pauling s argument is that the metal atoms in the crystal have an available orbital to receive an extra electron and thus form an extra covalent bond, through a mechanism he called unsynchronized resonance. 

In the present chapter, we explore the Pauling ideas in the context of an ab initio valence bond formalism. We do so by admitting extra orbitals in the constituent atoms of molecular systems, and devising the new types of VB structures that can be set allowing the atoms to form more bonds than their atomic valences admit. We will see that these Pauling s structures, as we named them, are important to describe some kinds of delocalized bonds and that they give some information about possible processes of charge transfer in the molecular systems. 

---