Electronic structure calculations on a conjugated polymer chain by Hartree-Fock and density functional theory show a sequence of self-localized states, which stand in contrast to the single self-localized soliton state described by the Su-Schrieffer-Heeger model Hamiltonian. An extended Hubbard model, which treats electron-electron interactions up to second neighbors, is constructed to demonstr...

A strong generic coupling between self-localized solitons and conformations of a pi-conjugated polymer chain is demonstrated through ab initio calculations and the underlying mechanisms revealed by using an extended Hubbard model. We show that significant chain bending and twisting of trans- and cis-polyacetylene result from torque imbalances among atom-centered orbitals and the steric instabil...

2014 Dielectric measurements were performed in a large frequency range (10-4-10+5 Hz) on undoped cis-polyacetylene samples from several laboratories both with ohmic and blocking contacts. The carrier density is low (2 1016 cm-3) and constant but the mobility is thermally activated with a sample and contact dependent activation energy. A maximum activation energy of about 1.6 eV has been found w...

We identify excitonic confinement in one-dimensional molecular chains (i.e., polyacetylene and H2) as the main driving force for the saturation of the chain polarizability as a function of the number of molecular units. This conclusion is based on first principles time-dependent density-functional theory calculations using a recently developed exchange-correlation kernel that accounts for excit...

The Gross-Neveu model with chemical potential is investigated as a lowenergy effective theory of polyacetylene. In particular, we focus on the abrupt change in the features of electric conductivity such as sharp rise in the Pauli paramagnetism at dopant concentration of about 6%. We will try to explain it by the finite density phase transition in the Gross-Neveu model. The thermodynamic Bethe a...

A recently proposed ab initio Hartree-Fock approach aimed at directly obtaining the Wannier functions of a crystalline insulator is applied to polymers. The systems considered are the LiH chain and trans-polyacetylene. In addition to being the first application of our approach to one-dimensional systems, this work also demonstrates its applicability to covalent systems. Both minimal as well as ...

Two transferable physical parameters are incorporated into the Su-Schrieffer-Heeger Hamiltonian to model conducting polymers beyond polyacetylene: the parameter γ scales the electron-phonon coupling strength in aromatic rings and the other parameter ε specifies the heterogeneous core charges. This generic Hamiltonian predicts the fundamental band gaps of polythiophene, polypyrrole, polyfuran, p...