[en] Raman intensity of intramolecular and lattice modes of crystalline alpha-bithiophene (alpha-2T) are investigated within density functional theory using a nonlinear response formalism. First, comparison between the calculated Raman spectrum and the experimental data allows the assignment of the main Raman lines over the whole frequency range. Then, a bond polarizability (BP) model, limited to first neighbors, is built. We show that, although the BP model cannot reproduce the changes of dielectric susceptibility under individual atomic displacements, it is accurate enough to reproduce the profile of the unpolarized nonresonant Raman spectrum of alpha-2T powder. Finally, the BP model, fitted on our first-principles results on alpha-2T, is applied with success to the alpha-quaterthiophene polymorph phases and alpha-sexithiophene, demonstrating on practical examples that first-principles and BP approaches are powerful complementary tools to calculate the nonresonant Raman spectrum of alpha-2T and make reasonable predictions on larger oligothiophenes.
Disciplines :
Physics Chemistry
Author, co-author :
Hermet, P.
Izard, N.
Rahmani, A.
Ghosez, Philippe ; Université de Liège - ULiège > Département de physique > Physique théorique des matériaux
Language :
English
Title :
Raman scattering in crystalline oligothiophenes: A comparison between density functional theory and bond polarizability model
Publication date :
14 December 2006
Journal title :
Journal of Physical Chemistry B
ISSN :
1520-6106
eISSN :
1520-5207
Publisher :
Amer Chemical Soc, Washington, United States - Washington
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