Journal of Chemical Physics
We utilize the Pariser-Parr-Pople model for poly (phenylene vinylene) (PPV) and take into account the realistic lattice structures of PPV considering the electron-electron and the electron-phonon interactions so that we can expose the subtle electronic and the lattice structures of PPV. We find that the lattice deformation is mainly in the vinylene group, and we also discuss the spin density waves of polaron and the charge density waves of polaron and bipolaron. The spin density wave is modulated by charge density wave. The competition between polaron and bipolaron are studied. We find that when the electron-phonon interaction lambda <0.21 and the intersite electron-electron interaction v is comparably small, v favors the polaron. When lambda >0.21, v favors the bipolaron. (C) 2001 American Institute of Physics.
关键词:
conjugated polymers;poly(para-phenylene vinylene);poly(p-phenylene;vinylene);ground-state;absorption;exciton;polyacetylene;model;polypyrrole;singlet
Communications in Theoretical Physics
The electronic and lattice structures of poly (phenylene vinylene) (PPV) are studied theoretically. Both the electron-electron and electron-phonon interactions are taken into account in the Pariser-Parr-Pople model. The electronic band and the lattice structure of the ground state and the polaronic state are calculated by means of the unrestricted Hartree-Fock method. In the ground state, there exist eight bands in PPV including four valence bands and four conduction bands, and the benzenes can be considered to be rigid. The polaron induces the split of energy bands. There are four localized electronic states within the energy gap. The defect of the polaron appears to extend over about 5 units. The benzenes are strongly affected by the electron-phonon interaction. Our calculation for the energy band structure of the ground and polaron states are consistent with experimental absorption spectra. The results of our calculation show that the electron-phonon and inter-site electron-electron interactions play an important role in determining the electronic and lattice structures.
关键词:
electronic structure;polaron state;PPV;benzenes;conjugated polymers;trans-stilbene;poly(p-phenylene vinylene);conducting polymers;band-gap;triplet;absorption;poly(para-phenylenevinylene);excitons;singlet
