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Durham University

Department of Physics

Staff profile

Publication details for Professor Stewart Clark

Zheng, G, Clark, SJ, Brand, S & Abram, RA (2006). Lattice dynamics of polyaniline and poly(p-pyridyl vinyline): First-principles determination. Physical Review B 74(16): 165210.

Author(s) from Durham


First-principles density functional studies of the dynamical properties
of the conjugated polymers polyaniline and poly(p-pyridyl vinyline) are
presented in this work. We have employed linear response within density
functional perturbation theory, as implemented in the CASTEP code, to
investigate the Born effective charges, polarizabilities, and
vibrational properties. With regard to the last, we have calculated the
vibrational frequencies and made assignments of the modes for the two
polymers. Most of the phonon modes have been classified and we have
shown that the higher frequency modes are associated with C - H and C =
N stretching modes. We also present the results of calculations of the
polarizability and permittivity of the materials which are in
reasonable agreement with the typical values of conjugated polymers.
Dynamical Born effective charges have been calculated and compared with
the Mulliken population atomic charges. It is found that notable
differences exist between the Born effective charges for the nitrogen
atoms in the conducting polymers, and we conclude that effective
charges are more appropriate for use in the study of the dynamics of
the systems. Differences are found in the ir absorption spectra
obtained for the two polymers, which can be attributed to the
structural differences of the two materials. It is found that the
presence of the nitrogen atom plays an important role in determining
their lattice dynamics.