Asian Journal of Physics  Vol. 31 No 2, 2022, 211-225

Infrared active vibrations in doped π-conjugated materials: the mechanism of activation of Raman modes
C Castiglioni and M Tommasini


We present here a theoretical investigation on the effect of doping polyacetylene with electron acceptor/donor species. Density Functional Theory (DFT) calculations, applied to selected molecular models, allow describing the response to the charge transfer, which highlights remarkable physical effects, like the relaxation of the molecular geometry and the softening of the vibrational frequencies. The analysis of the predicted spectroscopic observables gives insight about the origin of the strong doping-induced IR vibrational transitions, closely related to the major Raman bands of the undoped species. The analysis of the infrared intensities through local contributions based on electro-optical parameters reveals that intramolecular charge hopping is promoted by collective nuclear displacements along the Effective Conjugation Coordinate (ECC). © Anita Publications. All rights reserved.
Keywords: Polyacetylene, conducting polymers, doping, polaron, soliton, DFT simulations.

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