Quantum and Classical Studies of Calcium and Zinc Clusters and of Pyrrole Oligomers

Polypyrrole (PPy) is a conjugated polymer prototype of conducting polymers. The energetically preferred spatial conformation and charge distribution of n-Py oligomers (n = 1--24) in both the reduced and oxidized phases are obtained and analyzed in this work within the hybrid density functional theory. Binding energies, HOMO-LUMO gap energies, radius of gyration, end-to-end distance and vibrational frequencies are reported as a function of oligomer length. The band structure of infinite PPy gives a band gap energy in excellent agreement with experiment for reduced PPy. Evolution of the band gap and the charge-localized states as a function of PPy oxidation level is reported.