We present a self-consistent field algorithm for the restricted open-shell Kohn-Sham method which can be used to calculate excited states that have the same spatial symmetry as the corresponding ground states. The method is applied to -* transitions in polyenes, cyanines, and protonated imines. Excitation energies obtained with gradient corrected functionals are found to be significantly redshifted; the shift is constant within a homologous series. Planar excited state geometries have been optimized for all systems.

We present a first-principles molecular dynamics study of the excited-state motion in a molecule that has recently been proven to exhibit light-driven unidirectional rotation. The simulations show that the directed motion is due to the complex excited-state dynamics on ultrashort timescales in the chiral system.

We present first principles molecular dynamics simulations of the photochemistry of butadiene and cyclohexadiene. The excited state is described with restricted open-shell Kohn–Sham theory. We observe cis–trans isomerizations for 1,3-butadiene and conrotatory ring opening of cyclohexadiene. The excitation of a sample of several butadiene molecules leads to the formation of an excimer.

Quantum chemical calculations of undistorted poly(phenylene vinylene) chains at zero temperature exhibit chromophores which are delocalized over the whole polymer. We demonstrate with molecular dynamics simulations that chromophore localization in agreement with experiment can be obtained if the system is simulated at finite temperature. The dependence of the chromophore localization on the temperature is investigated.