Binding description

Approaches based on conductance calculations. More direct, these approaches focus in the measured quantity the conductance. There are two main groups of theories. One is based on a tight-binding description of the transport processes where the electron current jij between to adjacent sites i and j, is evaluated by using [26-28] ... 

Despite our ability to now write down with some level of confidence the tight-binding description, our treatment has been overly cavalier in that we have as yet not stated how one might go about determining the Hamiltonian matrix elements, h f. Note that in precise terms these matrix elements describe the... 

For metallic single-wall carbon nanotubes the free-electron model of electronic structure with finite thickness of the conducting shell is proposed. The band stmcture calculations in the frame of this model of armchair (n,n) nanotubes (for n = 5-10) show essential similarity with tight-binding description. 

Whereas the Frenkel tight-binding description is valid for excitons localized to atomic dimensions, the Wannier approximation describes excitons delocalized over many lattice distances. The hydrogen-like wave functions associated with these states serve as envelope functions describing average probability in spatial regions of lattice-constant dimensions. 

This schematic figure sketches differences in the metal valence band electron density structure based on a tight-binding description with one atomic orbital per metal atom [17]. For the generalization to d-atomic orbitals, we refer to [36]. 

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