Zheng, Guang and Clark, S.J. and Tulip, P.R. and Brand, S. and Abram, R.A. (2005) 'Ab initio dynamics study of poly-para-phenylene vinylene.', Journal of chemical physics., 123 (2). 024904 .
We present an ab initio dynamics investigation within a density-functional perturbation theory framework of the properties of the conjugated polymer poly-para-phenylene vinylene (PPV) in both the isolated chain and crystalline states. The calculated results show that for an isolated chain, most of the vibrational modes correspond to experimentally observed modes in crystalline PPV. However, additional hitherto unidentified modes have been observed in experiment and our calculations on crystalline material have allowed us to assign these. We also present the results of calculations of the polarizability and permittivity tensors of the material, which are in reasonable agreement with the typical values for conjugated polymers. Dynamical Born effective charges [ S. Baroni, S. de Gironcoli, A. Dal Corso, and P. Giannozzi, Rev. Mod. Phys. 73, 515 (2001) ] are calculated and compared with atomic charges obtained from Mulliken population analysis [ M. D. Segall, C. J. Pickard, R. Shah, and M. C. Payne, Mol. Phys. 89, 571 (1996) ] and we conclude that effective charges are more appropriate for use in the study of the dynamics of the system. Notable differences are found in the infrared-absorption spectra obtained for the isolated chain and crystalline states, which can be attributed to the differences in the crystalline packing effects, which clearly play a key role in influencing the lattice dynamics of PPV.
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|Publisher statement:||Copyright (2005) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Zheng, Guang and Clark, S.J. and Tulip, P.R. and Brand, S. and Abram, R.A. (2005) 'Ab initio dynamics study of poly-para-phenylene vinylene.', Journal of chemical physics., 123 (2). 024904 and may be found at http://dx.doi.org/10.1063/1.1955516|
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