Poly valence effective hamiltonian calculation

Martin et as part of a combined experimental and theoretical study of a series of monodisperse capped poly(triacetylene) oligomers, have calculated their y-hyperpolarizabilites by a method which combines the use of a Valence Effective Hamiltonian with a SOS procedure. 

Poly(/7-phenylenevinylene) may be considered a regular copolymer of acetylene and benzene [128]. Electron structures of PA, poly(p-phenylene), and poly(p-phenylenevinylene) were studied by using UV photoelectron spectroscopy and quantum chemical calculations based on the valence effective Hamiltonian method. Excellent agreement between the theory and experiment allows a detailed description of the evolution of the electron structure in this polymer series. 

Let us suppose an infinite nondegenerate polymer chain (e.g., polythiophene) doped heavily with electron acceptors. At a high dopant content, the polymer-chain structure and electronic structure of the doped polymer are radically different from those of the intact polymer. As typical cases, we will describe two kinds of lattice structures of doped polythiophene (dopant content, 25 mole% per thiophene ring) a polaron lattice and a bipolaron lattice. They are the regular infinite arrays of polarons and bipolarons. The schematic polymer-chain structures are shown in Figure 4-16. Band-structure calculations have been performed for polaron and/or bipolaron lattices of poly(p-phenylene) [124], polypyrrole [124], polyaniline [125], polythiophene [124, 126], and poly( p-phenylenevinylene) [127], with the valence-effective Hamiltonian pseudopotential method on the basis of geometries obtained by MO methods. The schematic electronic band structures shown in Figure 4-17... 

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