Excited states of the of the double-stranded DNA model (A)$_{ 12}\cdot$(T)_{ 12} were calculated in the framework of the exciton theory. The off-diagonal elements of the exciton matrix were calculated using the transition densities and ideal dipole approximation associated with the lowest energy $\pi\pi^{ *}$ excitations of the individual nucleobases obtained from TDDFT calculations. The values of the coupling calculated with the transition density cubes (TDC) and ideal-dipole approximation (IDA) methods were found significantly different for the small inter-chromophore distances. It was shown that the IDA overestimates the coupling significantly. The effects of the structural fluctuations were incorporated by averaging the properties of the excited states over a large number of conformations obtained from the MD simulations.
Categories: cond-mat.soft