Interactions itinerant electron

The reduced orbital overlap between the radicals reduces the bandwidth and the electronic structures could be better considered as those of a localised rather than itinerant electron system. This poor overlap results in very small antiferromagnetic interactions being observed, and the compounds behave as nearly perfect Curie-Weiss paramagnets. In the cases when improved lateral interactions between the stacks are achieved by change of the substituents85 the compounds behave as weak ID ferromagnets due to the effective orthogonality of the S C interactions. 

Fig. 2 Representation of the ferromagnetic alignment of d localized spins resulting from the interaction with itinerant electrons through short intermolecular contacts...

Extrapolation of the rules for the sign of the superexchange interaction, eqs. (9) and (10), to itinerant-electron magnetism leads to the following rules for bands containing n electrons per band orbital (0 < n < 2 because of spin degeneracy) ... 

The transition from localized to itinerant electronic behavior occurs where the interatomic interactions become greater than the intraatomic interactions. A measure of the strength of the interatomic interactions is the bandwidth W and of the strength of the intraatomic interactions is the energy C/eff that separates successive redox energies. The transition from localized to itinerant electronic behavior occurs where... 

The temperature dependence of the NMR relaxation rate Tf1 for the Au compound (Fig. 9) exhibits a typical behavior of one-dimensional conductors with deviations to the Korringa law (Tf1 T) shown by the upward curvature at high temperatures similarly to (TMTTF)2PF6 [41] and TTF[Ni(dmit)2] [42]. Since there are no localized spins on the dithiolate chain, the relaxation comes from the hyperfine contact and dipolar interactions, 7 1 + r j, produced by the spins of the itinerant electrons along the perylene stacks. The enhancement of the relaxation is, however, less important than that shown by the Bechgaard salts [45]. 

It is often said that the band description of one-electron states is in terms of itinerant electrons and is mainly useful for solids, while the bond description looks at localized electrons and is appropriate for molecules. Since our subject concerns interactions between molecules and solid surfaces, we need to establish our vocabulary clearly. We will consider an electron as localized if it cannot participate in (electrical) transport phenomena otherwise it is itinerant. This is not the same as describing the one-electron orbitals by localized functions (such as the Wannier functions, introduced below) respectively by extended functions (such as the Bloch functions, see below). Nor is it simply a distinction between tight-binding orbitals constructed from (so-called localized) J-orbitals as opposed to those derived from (so-called extended) -orbitals. 

---