Base and salt 3D forms of Emeraldine II polymers by Car-Parrinello molecular dynamics

We have studied structural and electronic properties of the three-dimensional crystalline regions of Emeraldine II polymers, in the base (EB-II) and salt (ES-II) forms, by means of first principle Car-Parrinello molecular dynamics. We compare the geometrical structures of the polymer chains in the primitive cells of EB-II and ES-II, pointing out the structural effects due to the protonation with HCl of the iminic nitrogens in the EB-II chains, and the effect of the counterions between neighboring chains. We also analyze the HOMO electron density distribution, band structure and density of states of the resulting bipolaronic structure of ES-II, which is energetically stable and maintains semiconductor character.