ELECTRON LIBRON COUPLING IN POLYANILINE

We investigate a one-band model with electron-libron coupling and a st eric potential in order to discuss the influence of phenyl-ring rotati ons on the electronic properties of pernigraniline, the fully oxidized form of polyaniline. The T = 0-ground-state phase diagram is mapped o ut, and it is shown that forward-scattering processes of electrons pla y an important role in the framework of this model. They lead to the p ossibility of a charge-separation ground-state. Adding a local Hubbard repulsion, we find a strong dimerization enhancement for weak U while in the large-U limit the Peierls ground-state can break down in a cer tain region of parameter space.