Toward Systematic Understanding of Diversity of Electronic Properties in Low-Dimensional Molecular Solids

The aim in this review is to search for a possible systematic theoretical understanding of particular electronic properties of the conducting A2B compounds based on the frontier orbitals, HOMO and LUMO. The main interests will be (1) How are the metallic states realized? and (2) What kinds of ground states are expected in each case? The basic Hamiltonian to examine this problem will be the tight-binding model based on either HOMO or LUMO of relevant molecules together with Coulomb interaction not only within the same site, U, but also between neighboring sites, Vij, as well.