Static and dynamic polarizabilities of oligothiophenes

Abstract

A comparative study of static and dynamical polarizabilities of small oligothiophenes until the hexamer is performed employing gradient-corrected and hybrid functionals within auxiliary density functional theory. Because the dynamical polarizabilities are calculated at the experimental wavelength of 589 nm, a direct comparison between experiment and theory is possible. For the smaller oligothiophenes until the tetramer, very good agreement between theory and experiment was found. The calculated dynamical polarizabilities of the pentamer and hexamer oligothiophenes are affected by a too low-lying excited state due to the employed gradient-corrected functional. It is shown that this artificial pole affects mainly the longitudinal component of the polarizability tensor. Our analysis suggests that success and failure of gradient-corrected functionals in the calculation of dynamical polarizabilities depend critical on the corresponding Kohn–Sham eigenvalue spectrum.